[suicideneil]

Definately check your radio and esc settings, might be worth going through them again and looking at the epa and such. On the esc, plug it into the castlelink ( if you have one, if not buy one ) and tweak a few things:

Punch control needs to go down to make the motor more punchy, so if its at 100% set it to maybe 50% and try it again.
Start power is fine on low or medium-low
Timing is best left on low.
Maybe check the throttle curve to make sure its normal- diagonal line.

Traction and slipper settings will play a large part too, but I've seen plenty of box-stock Fluxs do standing backflips and wheelies on 4s lipo, so take a look at those too.