8s stutters w/9920

[rkman]

I got an 8s and 9920 from Mike and I set it up but when I hit full trhottle from a stand still or slow roll it stalls and doesn't go.

If I slowly throttle up the truck will accelerate ok. I have this in a stampede running 6 & 7 cells. I also have a UBEC installed. Is this a function of the low cell count or something more serious?

The 9920 is going in my E-maxx eventually and I'm looking ant the MGM 80 or 120 to put in the stampede.

Thanks in advance, you guys have provided me with much appreciated help.