So my original answer is correct, it’s purely down to the testers discretion. It could pass or fail.
There was indeed a publicised MOT failure of a BBR car whereby the tester noted one cat had been removed. The owner of the car went back to BBR and they offered him a manifold with a cat on it.
BBR are doing exactly what I would do in this situation; lay the facts and the products on the table and let the buyer make the decision based on that.
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If the design of the exhaust uses one catalyst where there were originally two, this is not necessarily an MOT failure, provided the system still meets the same standard for noise and emissions as the OE components did when in a serviceable condition. It may be necessary to show a receipt or other documentation to prove this, but like you say, most testers will not know how many catalysts were originally fitted.
Not from what I received.
You can’t just use your discretion to suit your own needs.
You HAVE to read the information as one and not pick bits out of it.
You test the car as presented to the current emissions standards and if it meets them they can’t fail it, discretion or not.
You can’t fail it because one has been removed as that is in black and white.
As I have stated not all testers may not know that MX5’s have 2.(as agreed by DVSA).
You can’t apply prior knowledge to the current presented test.
As long as the car meets the emissions standard then its irrelevant how many catalytic converters are fitted.
End of in my opinion.
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The post and the rules as they are written, then verbally explained contradicts itself in many ways, it is absolutely down to the tester how he wants to interpret the rules.
I give up. 
Thanks all for your help and very detailed answers following up.
I’m going to go for the catted manifold just to be on the safe side. Saves any potential future headache down the road looking at how divisive this topic has proved to be.
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I think that in reality you can take the car to one MOT tester and he will pass it and another may fail it. This is down to being subjective and this will never change.
When I had a Lotus Elise, bought from Christopher Neil in Northwich (who I am buying my ND from), I got a sports exhaust with the cat taken off. I took it back to them to MOT it a couple of times before I got rid of it. They had said that they should refit the cat before testing it, but never did (I left it in the boot when dropping it off for the MOT). However it passed its MOT.
I doubt yo will get an answer to this question that will be 100% accurate to all MOT stations. However if you are going to take the car to one station and they pass it, then thats fine. However if you sell the car and the new owner takes it somewhere else, they may have a problem.
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Not like DVSA to avoid giving a straight answer lol
The MOT tester is always left to take the can
I have the bbr 200 pack with the decat manifold. I’ve only put it through one MOT but the previous owner put it through a few as well, never failed.
With regards to the actual performance benefit, its very much a gentle improvement - you know it has more power at the top end and the throttle response is better when you are in the in the right gear and you see the speed increasing faster etc which is all nice - you can see the clear improvement.
BUT, if you want it to actually feel noticeably faster, if you want to actually feel a much more pronounced shove into the seat etc, my experience is the 200 pack does not quite deliver it. The results are certainly there and I’ve no doubt in the engineering and the output etc, but for me the sensation of acceleration didn’t improve very much so if that’s what you want then my experience is you need to look at FI or see if you can take their ITB car out for a drive.
That’s interesting feedback, as I’m sat pondering the Super 200 pack too. The upgrade would be ~15hp for ££££s (currently have 189hp with their 185 kit). I sense that the step up would feel the equivalent of running the car on half a tank of fuel and without a passenger.
That said, I did notice the things you mention in taking the step from standard to the 185 kit. The sensation of acceleration definitely aided by the sportier rear (not so) “silencer”!
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This is excellent feedback - thanks - I was considering a chip upgrade, but this may offer even less of an “improvement”…
I would be after the sensation more than anything, which is why I have ordered my new ND with the factory sports exhaust and sports suspension… going quick in itself is not necessarily fun, it is the engagement. all things considered, I will leave the chip upgrade, especially as it could have warranty implications.
It’s all down to cost, you get what you pay for.
Having driven many NCs at different power levels I think that +40bhp is a fairly big increase for what it is, it’s certainly very noticeable on a car the size and weight of an MX5.
Naturally aspirated tuning is always expensive for relatively little gains when comparing to a turbo.
You also have to question why you would want so much more power in a road car. Personally I drive bone stock vehicles as my own daily drives, I don’t see the need for anymore power or to be polluting the atmosphere we live in, I can’t use it on today’s roads anyhow.
I think a lot of it is mainly for d1ck waving purposes on the internet.
If you’re talking about a track car then it makes more sense, but then again so does learning how to drive the thing properly.
I’ve written about the subject at length before now on my Blog.
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I’ve had 400hp in an NB but feel 207 is “just right” in my BBR200.
That’s because you’ve never driven a 2.5 NC, it’s even more ‘just right’ 
Alex,
Exact same car, mileage and consideration for the BBR 200. Engine is holding well, but I don’t know how much of a beating it handled with its previous owners (and tbh I take it to the track, not like I am the smoothest owner lol).
Curiosity: has anyone here quoted for the “disaster scenario”? Any firms providing reliable 2.0 NC replacement, or anyone that had experience with that to provide a rough £ estimate?
Thank you
I’ve had quotes for £2,500 to £3,000 for a full 2.0 engine rebuild and I’ve seen a firm offering 2.5l swaps for £3,000.
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Was that a quote for car in, car out (from disassembly, rebuild and reassembly)? Seems reasonable to be honest. And assuming the camshafts survive, you wouldn’t lose the money of the BBR 200… interesting
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Yeah that’s drop off and collect I believe. Saving to get that done at the moment. 
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I am really interested in this BBR200 pack, mine is a 2006 2.0sport and i love it but sometimes would like a little more ooomph where safe to do so. The stats say 0-60 is 7.9secs standard and my question is how much would a 200pack reduce this figure?
If its not on their website, there are online calculators for that kind of thing.
dunno what the 0 to 60 is but i have it on mine and its worth doing its more responsive and quicker right through the range
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