Thanks for the reply Cpt.
On the Bench with the wheels off the ground, it accelerates and brakes fine.
Seems normal.
I've tested the diff tightness. I hold the spur and right tire while checking to see if the left wheel will slip. It barely slips. I tightened down just a little.
When I do a quick test - it would run ok if started slow and gradually speed up. But when you just blip the throttle it would slip.
I've adjusted the slipper to almost full lock and does the same.
I will try to go to the track today and do more testing.
No, that's not what I mean. You need to test how tight both your diff and your slipper are. Get the car ready to race, and set it on it's tires on the bench/table. Hold the right tire tight with your right hand, and hold the left tire tight at the same time you are holding your radio (can be a bit tricky)... With both tires held right, blip the trigger full throttle for a fraction of a second. Does the diff slip? does the slipper slip? do the front wheels come off the ground? You need to set it so that the diff does NOT slip, but the slipper does. But the slipper should only slip the TINIEST bit... it should still grab enough to pull the front tires off the ground.