hey your truck is a CEN, so your realy lucky, because when you go to the car forum, go all the way down to http://www.rcuniverse.com/forum/RC_C...mid_309/tt.htm and then click CEN. if that dont help take it to your LHS and tell them what wrong and see if they can fix it.
the only thing i can think thats wrong is the setting, or the carb is expanding alot since its probaly aluminum.