The TT 91 is one of the more powerful of the 90 class 4-stroke engines (excluding YS) but have a little longer break in time. One other thing is you need to have the choke installed on the engine. It acts as a ventury for the engine and you won't get it to run very well with out it so I have been told. Once you do have it boke-in you will have a real power house engine. I too agree with a65l but if you can't get the idle down a little, Maybe a little leaner on the low end might be needed, TT does not always have there new engines set well but do make a great engine.

Dauntae