You’re probably right about the 90% part. I’m in the 10% . Also agree that a lot of off the shelf kits and prevent like summit or flowmaster probably have fitment issues, however, I’ve yet to gave an issue with tti or accurate exhaust…. Well except once I did and sam at tti sent me a replacement part asap and issue gone. Worth the admission price to get the stuff for me anyway, especially for aftercare service