Ok my 99WR400F seems to run strong even in a little bit of elevation. I have noticed that when I am crusing like down a hill or grade and I let off the gas it pops and backfires just a little bit. Two of my friends, who know a little about 2 strokes and nothing about thumpers say that I need to adjust the fuel screw, and that I am running too lean. I know that I hear other bikes do the same thing so I am not to worried about it. I have a pipe, headers, and rejet. Throttle stop gone, air box cover removed, but grey wire still intact. Am I running too lean? Should I spend the money and buy a new fuel screw so that I can change the mix on the go? I always heard a little backfire pop is not such a bad thing. Am I missing something?