nope, they're sh*t and pointless.
fitted one on the car about 10 months ago now, re-tuned it every month, so know it was set right, and really was pointless. All it did was rasp and whistle when the car was warm and made the car sound like there was a broken child's recorder wedged somewhere in the engine-bay - not the best sound out of your nice coupe...
a bigger worry is, if it's out of tune it screws with your brakes
A fellow coupe owner (Fugazi? cant remember) found his brakes become very spongey with it fitted - so i de-tuned mine and could replicate. So, erm, not that great...
Also read a few law reports about how the company has been taken to court regarding their claims and they've not been able to uphold any of them for a modern-day car. Only claim they managed to get away with was the "new" statement, and they got away with that due to a new colour-scheme, or something daft like that. Fancy some reading:
2 reviews of cases of false-advertising regarding the claims:
& - note the complaints against them were upheld throughout... ie - unable to prove any power or mpg increase...
tbh, after 6months fitted I noticed no benefit and got sick of the sound so closed it off. If i had a spare length of tube I'ld remove completely (and may well ask garage to when it's service time).
There's a few posts about in on the forum and general view is to not waste your cash (and quite surprised it's even in the diy section tbh).
