faulty plugs yep yep, check for exhaust leaks, loose header/ bad gasket.. stuff like that.i had this one header for as long as i had my gt. i got the gt when it was a tub chassis. i guess it got warped for using it so much different engines and stuff. anyways it ended up having a permanent leak witch in return over heated my engine and burnt the piston and sleeve. on 2 engines lucky me there was no parts for a .18wasp so i got a .15cv that burnt up too. i thought it was my fault . i almost cried i burnt 2 engines and ive been doing this for how long i almost cried. so i checked everything out inspected it with a magnifing glass. i notice a carbon build up on the header "exhaust leak".. i went and got a new header but the cv burnt out quick one gallon it was done... i was breaking in the engines when i burnt them.. wierd but that leak was why. now i got an SH.12 for 129$ rear exhaust no room for errors! i love this engine