if your talking about the 3.3, how many tanks of fuel have you run thru it? my 3.3 ran ok for the 1st 3 tanks,then started running poor,i called traxxas, they said put a new glow plug in it,run a few tanks at med to high speeds,even if it bogs low to mid range. i did that,kept clearing out the exhaust,and after like 7 tanks, the engine started to run ok.they said it takes a good 15 tanks before it is totally broken in,it loaded up bad down ,but i still kept runnin it med to high speeds. lean the hsn ,then after thats set,start to lean the lsn. very important to install a new TRAXXAS glow plug after about 4 or 5 tanks. good luck