So a few weeks back I changed the induction kit for an aem Cai one running the piper catback that came with the car, and from memory it ran fine. It may coincidence but since fitting the sportex silenced bpipe and n1 rep backbox every now and then I get like a 'stutter/hesitation' accelerating low down (not quickly may I add). It feels as though its popping too slowing down, hard to describe really lol.