I always thought the popping and banging was the unburnt fuel ignighting in the exhaust personally I like it, google focus st and mountune it sounds fantastic. Oh a d pipeworx get very good reviews and I've had a jetex system in the past and it was very well built
Yeah I believe it is uncombusted fuel igniting as it's fired through the exhaust. My car is running rich at the moment and will probably be why I'm getting a lot of the pops etc. I do like it, it's not chavy because chavs can't recreate that noise... they're more into their deep rumbles