im guessing you didnt get what he said. when you put on the body, it is pressing on the fuel line and when you go WOT it wants more fuel.
a while ago with an onroad car i think it was a hpi rs4 3 nitro, anyway i put a new body on that had no vent holes in it and it would cut out. and without the body it would go nice.

btw what car are you talking about