I have a Futaba 3PK with a Spektrum system in it and I am running lipo rec. pack and Hitec 5955TG servos,this is in my Mugen MBX6. The last race I ran on the back straight it is a big triple you have to do as a double-single.
Anyway every now and then when I would get ready to blip it to clear the single it either would go full throttle or not let off the gas soon enough, some times it was fine? No problems with steering!
I just put some slicks on it and ran it down my road blipping all the way the farther I got away the slower the response got, I know it takes a little more time to travel that distance but you shouldn't be able to see the differance.
Could the throttl servo be going bad?