Howdy, hopefully someone can drop some knowledge on me. Please try to follow as im not much of a writer, im probably going to be all over the place....bear with me. I installed a custom "FLOWPRO" fcr mx 39 on a drz400sm :"3x3 & full GPR exhaus, no tps connected" WOT it runs and pulls perfectly, as expected. 1/8th-1/4 its sputtering like crazy or if im just cruising at a constant speed after a second or two it spudders until i crack it open. I had the A/f mixture screw and 2-3 turns out and it was sputtering like crazy anywhere from 1/8th throttle to 1/4th or just cruising at a constant speed. So i turned it all the way in and it ran much better, but its still happening, which leads me to believe it is too rich? I ran it without the airbox and it ran better that with it on there but not a significant difference. It has a new air filter and sparkplug looks good. It was running perfectly this morning with the mikuni on. Jetting spec: Idle jet #40 Main jet #155 Main air jet #200 Idle air jet #75 Choke jet #75 Needle ELQ 4th clip from top, "was on third but ran much worse, the guy that built it said to drop it one more clip to see if that helps, It did help a good bit but still not perfect" other than the spudder at 1/8 throttle and having to have the AF all the way in it runs great. WTF. I tried to give as much info as possible, let me know if theres anything i missed.