The pilot is probably a little lean (the popping on decel) and the black smoke and bog usually come from the momentary rich condition generated by the accelerator pump. Do a search for BK mod, it's a quick/cheap mod that allows you to tune the accelerator pump duration to eliminate the bog (and probably the black smoke puff). Be careful with richening the pilot circuit though, especially if the popping only occurs at high revs (as you're decelerating). If you make it rich enough that the high rev decel doesn't pop at all, it may be too rich at idle and during slow rev acceleration. One of the common comments on this board is the stock jetting is too lean. It may not be at your altitude, but it wouldnt' hurt to try going up 1-2 sizes on your main jet and see if it pulls any harder up top. Thankfully main and pilot jets are cheap and relatively easy to get to on this bike. My 2000 came with a 162 stock but also came with a 158 and 168 main jets. Be sure to write down the env. conditions (temp, humidity, elevation) and the jets you try each time. That way you'll build a little database about what works best for your bike under what conditions. Also, try doing only 1 thing at a time, that way the different changes don't get convoluted.