i have a 04 crf100 that i have just picked up it has a FMF powercore 4 exhaust. I had posted about the idling issue i was having and the back firing during deceleration. I plan on buying a 38, 40 pilot jet and a 100, 102, 105 main jet to tune it. Today I did some basic maintenance on it like changing the oil and cleaning the air filter. The air filter seemed to be pretty dirty but i have seen much worse (during cleaning some of the foam on the dirty side started to peel off and it will need replacing), i was wondering what is the most efficient air intake mod? I would like to maintain the oem air box but do must people just hook up a uni filter right to the carb? also some silly questions like is the bbr rev box worth it of just a gimmick?