Is it the engine or is it the clutch??
When I first put my 1/8 scale buggy on the track it has a lot of snap/punch on the low end but once its warmed up after a few laps the snap/punch is not like it was its a lot milder. I'm running the Werks B5 and the Jammin red aluminum clutch shoes and the 1.1 springs that came with the clutch shoes. The motor has a little over a half gallon through it so I'm thinking that maybe its the clutch??