whynot

Hi, new here and some questions. Just bought a 01 banshee, it came with fmf sst pipes and fatboy II silencers, k&n air filters with outer wears, stock everything else. It starts and idles smooth, but feels like it loads up just before the powerband kicks in, and the power flattens out at 3/4 throttle and above. The left plug is dark brown/black on one side of the porcelain and whitish on the other side, and the right side is dark brown/black all the way around. I have not checked what it is jetted with yet. I live at 4,000ft elevation and the temp.is around the 50's, humidity what humidity in the desert. Lol. Thanks for all your help in advanced. Ty