i also have an IL MotorSport back box.
i am very happy with the sound.
it gives a deeper more satisfying note without the extra volume.
my only grumble is that unlike on B_W’s my tail pipes dont stick out the back like his.
my tail pipes need to be about 1 and a half inch longer!
IL is a nice one indeed…about pipes sticking out; i believe (not sure) that when i bought it i had the choice between NC1 and NC 3.5/3.75 option believe this might be because of the different designs of both bumpers.
NC backboxes are pretty expensive also and don’t give much of a power gain without a retune, making it a lot more expensive 
Obviously another header will not give the best result without a remap but even without a remap the effect is very noticable. If the only target is better power, torque and driveability I would not spend the money on a backbox alone.
thank you.
i though i was going abit mad. as the new backbox does seem to have given my 5 abit of a boost.
guessing its boosted me by about 3 hp.
personally i didnt think a backbox would give any hp boost.
but sometimes it nice to be wrong.
Back box gives some performance gains if its completely unbaffled.
However biggest change would be the exhaust manifold. Removing catalyst’s instead of using high flow catalyst’s will also change the engine map. Not much change with just an exhaust mind but it would amplify the gains on modified engines.
On the other hand, we all know that each stripe is 7hp minimum 
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7 hp each bit for center and backbox! thats more than i expected i thought it was more like 3 to 5 hp each bit.
moving on
now that i am almost finished with the “stuff to do after buying to put things right list”
i am starting to think about the next steps.
right now i think my best move is to spend 14 hundred on the BBR 180 kit that will give me the high flow cat down pipe and a remap.
then i can either save for the 225 kit (cams and throttle bodies) or save for the supercharger.
which ever way i go they both require the downpipes.
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take it on a track a few times. you can then decide what you want to do /what the car needs next
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Great changing the back box on your car to make it louder, but, be warned many track days require your car to be below a certain dB level or they won’t let you go on the track
Quite simply, they have to “look” right and “sound” right. They also have to be well made. The cobalt did it for me. 
I worked in a dealership years ago which was taken over so there was surplus stock including this Sebring back box. It’s subtle but has a good tune on acceleration and pops and burbles on deceleration and changing down. Not in a loud way but puts a smile on your face.
Not sure they are still available but I couldn’t say no to £50 ex stock 
As long as it has one (and its not straight through pipes) it be fine
I like the sound of the cobalt I have on my NC1. Couldn’t compare it to anything else, as it came on the car, but it’s decently loud. Certainly I wouldn’t want it any louder as it would ■■■■ off the neighbours!
Wish it burbled a bit more I guess, but I think that may be more to do with other parts of the system.
Cobra race on my nc1, just the job for me.
No real drone inside cockpit, however cockpit was stripped out and soundproofed also boot soundproofed.
Even filled the voids of boot lid with expandable foam filler.
So now that iv had my il motorsport backbox on for a while i can give a better summation of it.
Drive wise its a loverly deep rumble.
Yes there is some drone at cruising speeds but it isnt loud or annoying and it doesnt take much radio volume to cover it entirely.
However.
It does give off a deep bass rumble that can be heard by people sitting in there house!!!
As iv previously mentioned i use my 5 for work as a pizza delivery guy.
I quite often get people meeting me at the door saying “i heard you pull up”.
Now one of my customers is an former “girl racer” and she says its a nice low rumble.
Also no one has complained so i guess its ok.
Sidenote back when i had the manta i did a few deliveries in that and people did complain about the exhaust noise.
That had a jetex downpipe and pmc center and backbox on it.
Right now tho im wondering what difference if any will changing from the standard down pipe and center section to the high flow BBR header and center section?
I know if worst happens i can buy a goodwin super quiet backbox but im really hoping i dont need to do that.
It will get louder again. As I daily mine I intend on keeping everything but the manifold oe, that way it’s enough to enjoy but not irritating.
I have replaced OEM mani for catless mani and mid pipe with sports cat. It doesn’t get that much louder, no drone. Sounds much better though, gives a veeeery slight burble sometimes on decelleration and the small amount that it is louder is very welcome. I would classify it as OEM+. So if you ever wish just a slight bit more or a bit more performance then I’d reckon mid pipe replacement is the next step if you already replaced your manifold.
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