Hi guys, I have on my S3 the following: XS/Pipewerx 3'' DP XS/Pipewerx 200 cell sports cat Milltek Resonated cat back Long story short, the sports cat reduces down from 3'' to between 2'' and 2.5'' iirc and sleeves into the Milltek system but for one reason or another the sleeving is incorrect and exhaust gases are blowing past, thus creating a whistle when throttle is applied. My plan is to modify the sports cat (cut back to the 3'' bore) and tig weld a 5ft straight stainless pipe all the way through to the rear silencer, thus removing the resonator box and most of the exhaust bends creating a 'straight through' centre section. My question is that if I am removing the exhaust bends, resonator and reducer within the sports cat (restriction) would i lose back pressure and ultimately lose power? I'm unsure as to why the sports cat reduces right down from 3'' but i presume this is so it fits the standard OEM cat back system and doesn't accomodate the Milltek. Can anyone shed any light on this? Thanks in advance. Shaun.