Ok, having some problems on decel. Instead of "coasting" when letting of the throttle, the bike seems to "engine break" causing me to lunge forward a bit. Lots of popping now on decel too. I've done a lot of research indicating an air leak in the header pipe as the probable cause. Question. the flange used to bolt the header to the engine sits about 1/2 away from the surface when the bolts have been tightening. Every other bike I have owned, this flange sat flush to the engine surface. Is this normal? Also, one of the bolts is a regular 10mm bolt while the other is a hex head requiring an allen wrench. Why is this? I can't get the other one as tight as the regular bolt. Is that my problem? I bought the bike used and this is the way it came. I bought a YZ muffler a while back and slipped it on to the stock header. Backfire on decel to too much to bear. Should I invest in a new header pipe? If so, should I get the YZ and match it up with the stock YZ exhaust or stick with stock WR header/muffler? Thanks in advance!