Co-op! Enjoyed the debate 
It’s a very grey area because as said above if you didn’t know for sure you would pass & possibly advise, the MOT course also says you ‘must not’ use product knowledge…so again if it was to have a cat and pass the emissions test on what grounds should it fail?
I’m not saying it’s right or wrong just a very grey area
Interesting indeed.
Well, at least we all agree on a very large grey area! 
I agree with all said my point was if you were unlucky to get a tester who knew and you just paid 200/400 pounds for a decat manifold and it failed your car is of the road not sure but I think it is recorded so you cannot take it to another tester trying to sneak it through, did not BBR offer to replace none cats they sold for there cat version if that happened then some customers most have been caught out…I guess if you were going to do it now are the cats fitted to the new manifolds dummies but for mot reasons it looks like you have one
Oh dear, got me a bit worried now, just had a BBR stage 2 fitted, Neil did say he had removed a Cat, but I’m not sure which one. He said it would pass the MOT but to make sure it was good and hot first. So even if it passes emissions it could still fail on not being standard?
Personally, I do NOT disagree with any of the comments.
Just trying to get the correct answer.
As Rodders/Robbie points out ‘must not’ use product knowledge…
As the paragraph states you only need to check components that are visible and identifiable.
Therefore, if you know it should have one but can’t see it, it therefore is not part of the test.
Is it difficult to see exactly what is there is another question.
‘must not’ use product knowledge…
So based on the above you are not allowed to fail it.
Is it daft?
Certainly very grey.
At some point you will need to take the car back for a retest “IF” it did fail.
Some stations are happy for a free re test, (some a partial fee) on the failed items within a certain period.
It is my understanding you can take it to any station for a test if you wish to pay again.
Various rules apply, so check with the Station or via various internet sites.
Any failure is recorded on the registered MOT Testers GOV data base, so they all know what the failure was.
If you didn’t know you can also check the history yourself on the GOV web site of ANY car.
It has to be done at some point.
I have no knowledge what BBR do or have done, just quoting what they have stated.
Perhaps you could ask BBR to authenticate the statement with evidence?
So, do we really know or have the definitive answer?
I would say no at this stage.
Do I still believe it’s all based on the emissions test?
Yes I do as that is exactly why the Cats are there.
The manifold (No matter who with) is a really great mod by the way and enjoy.
Well, there you go!
BBR are not being that Transparent are they. 
I suspect that he has fitted a 200 Cell sport Cat if he is telling you that. (Just an opinion).
Likewise, I would be a little bit annoyed that he has not told you exactly what he was gong to do and indeed had done.
EDIT- After paying that amount of money.
I am sure (well hopefully like us all) you don’t have any issues.
Thanks for telling us that.
Food for thought.
Just ask yourself this question.
How many cars (all makes and models) are out there that have been modified with either a header, modified stainless steel exhaust, (not as fitted) turbo, supercharger, cams, etc etc?
Should they have all been failed on the MOT test? of course not.
Insurance companies know the mods and as sure as eggs are eggs if they thought it was wrong they would be the first to tell you, “you were not insured”. (MOT Compliant).
We may never have a black and white answer.
Emissions still the key perhaps?
No problem.
Im sure Neil will sort it out. He has asked me to come back to sort out a back fire problem which he said might be sorted by going back to the standard exhaust system, so might sort out 2 problems with one stone.?
As you have asked.
Looking at the spec (Stage 1 and 2 Turbo I believe you mean?) I would say that the original exhaust system would just not work or fit with that set up without further work, hope I am wrong.
Not only that why would you want the stock stuff on there anyway. (only an opinion).
BBR are the supplier and state it’s “Legal”, so a matter for them really.
If I could justify and afford it I would do it too.
PERSONALLY, I wouldn’t worry about it and just enjoy it.
Pretty difficult to hang a turbo on the side of the original cat manifold.Bbr have probably fitted a freer flowing mid pipe and possibly back box. Both these items on the original car suppress the backfire noise. Once the ecu is recalibrated to fuel mods be they NA , Turbo or Supercharger the pops and bangs appear.
Yes Stage 2 turbo. It was Neils idea to go back to stock exhaust, so i guess he knows what he is doing. If i lose 20/30 BHP, so be it. I don’t mind the pops and bangs on full throttle but its when my other half is pottering down to Tescos its more of a problem.
Yes i certainly enjoy it, one of the few cars I’ve owned that i take out just to enjoy the drive.
Ive never been clear in my mind why this should be so. I had a turbo charged kit car with an Omex 600 and this never popped or banged at all despite getting near 100bhp more than standard.
We’ve all got the Tesco’s problem, (but mine is Sainsbury’s!). 
I bought an IL motorsports manifold in the end. I’m not that bothered regards to MOT as I can get thst sorted.
I believe an extra extension is needed for one of the sensors on the manifold though, on top of the one that is supplied with the manifold? I know it can be cut and wired but someone said you can buy the extension?
Davy_F, as Scarletpimpernel said I’m using the IL Motorsport manifold combined with a Cobalt rear silencer and not been for a tune. At the end of the day, its your choice to have the tune or not. For me it was justifying what I was getting for the extra £500 or so. I did find a Dyno map of this combo showing before and after tuning but unfortunately I didn’t bookmark the page and I’m struggling to find it again but if memory serves me correct I think the extra power gain was about 7bhp…I could have this wrong but I’ll have another search later.
For me having been using the car for a few weeks now with the roof down, I’m kinda thinking its borderline too loud for around town but the burbling sure is nice…
Adz, yes the pre-cat sensor cable wont be long enough. Easiest solution is probably to cut and re-solder some extensions in. The extension supplied is for the post-cat sensor which you will have to position as in the IL Motorsport diagram supplied with the manifold.
Good luck with the install. My advice would be take your time, if nothing else its all a bit fiddly!
It looks like BBR have tested their manifold against the racing beat one, https://bbrgti.com/products/bbr-4-1-mx-5-nc-manifold
The catted manifold is £714, quite hard to justify, as a manifold on a NC was a really cost effective way to gain power but at that price I’m having 2nd thoughts.
Does anyone know if it would be feasible to get the non-cat manifold and reattach the lower heat shields to the bottom of it, it may need a bit of fabrication but hopefully reduce the visibility in that area.
I see what you are doing!
Thanks to NC20 also for the link to BBR.
When you read what they say, it now seems they have changed the description of an instant MOT fail if a cat is removed. (On that link anyway).
They “Now say” DEPENDANT ON EMISSIONS.
Quite a bold statement to make now.
That has been my understanding all along.
Funny old world… 
DIRECT COPY FROM BBR SITE.
Please note. A change in MOT regulations May 2018 dictates that removal of a catalyst where fitted will now result in an MOT fail dependent on emissions readings. All non-catted MX-5 NC (BBR or otherwise) manifolds should be considered non MOT compliant.
I guess what that means if you buy a none cat manifold of them and it fails mot they are not responsible as they have stated it not mot campatible so no come back on them…