I have an 05 wr450. 170 main jet, stock pilot jet (45?) and use the blue needle in the 4th position. I'm no carb expert but it seems to run pretty darn well with the fmf factory 4 pipe. No problems in the past year. But that factory 4 might be the loudest and most obnoxious pipe ever. I just put the 96db quiet insert into it and repacked the muffler with the quiet packing. Its a LOT quieter now. But it doesn't run as good IMO. It starts up ok, but stalls very easily in first at low speed. Also, it seems to have a slight sputter or miss at higher rpms. It does sound a bit fat, but again,I don't exactly have a trained ear for these things. Common sense tells me that I should go with smaller jets since it is now more choked up. Should I go back to the stock settings and start the process over again? BTW... what are the stock mj, pj and needle settings?