I have a 2001 426 and just put on a FMF Q silencer with a FMF power bomb header and now have a real bad bog and rich burn at 1/4 to 1/2 throttle. I was running the same header with a white brothers e-series with 18 tuning discs and had no problems. I ride in central California around 1,000 ft elevation and 50 to 70 degrees temps. I tried to adjust the air screw in some which helped but not enough. I pulled my jets thinking they were larger than stock. (2nd owner) but I have 162 main and 42 pilot. I have not checked the neddle yet. The new pipe instruction did not say to change any jetting. I know that I have alot more backpressure now than before. Does anyone have any advise for me to hopefully eliminate some of my guesswork?