the piping being smaller from turbo to cooler is good so theres less pressure drop through the cooler. is this a new kit if so check and make sure nothing got in the piping or ic such as packing peanuts and stuff. check your A/R that should be stamped on the hot side on out side near entry bolt up to turbo or inside the exhaust entry square part where it bolt to manifold. you should need a .48-.63 to be all in by 3500-4500 with a stage 3 wheel! akso check shaft play up and down to see if the impeller on cold side is touching housing and check all couplers and BOV for boost leaks!