Full throttle NO GO!!

[RC-NUT]

Ok I'm stumped.

I have an MGM 8012 and a Feigao 8s running on (6) GP3300 cells. My stampede runs great up until FT where it cuts out completely. Anything over 75% throttle and there is total silence. However it will not do this if I hold the truck in my hand. (Only under a load)

So far I have:

1. Adjusted the timing and eventually went back to the auto setting.
2. Changed battery packs
3. Changed low battery cut-off point.

Any ideas?