Maybe not the one's you have but some do see thread by Hawkeye58:

http://rconline.community.everyone.n...rtOrder=descpl

Actually it's a problem with most 4 strokes but I suspect it is much worse on the TT 91. The carb is way oversized and will not have enough suction, the choke adapter is much smaller than the carb and without it you will deadstick after half a tank. But there is absolutely no RPM increase from 90% open to 100% open! This I know for sure cause I made the problem better by limiting the wide open throttle to 90%, but not enough. From about 60% to 90% there is only about 600 RPM decrease. Instant throttle response, just you can't notice the power decreasing until you move the stick down about 30% or more! Then it starts decreasing rapidly. Great power, in fact I don't think there is a more powerful 91 except YS.