YZ-2 Straight line stability

[Sean T]

I've run the YZ-2 for two meetings now, but cant find why im have problems with straight line stability. under heavy braking at the end of the straight the car pulls to the left every time, then as soon as i come of the brakes it will straighten up. then under hard acceleration at the start of the straight it pulls to the right. if i feed the power or brakes in very gently then there's no problem.
Im running kit setup apart from shock oils and springs, weight under lipo & 20g in front of servo, all of the transmission is free running with the gear diff with 3K oil, all the suspension is free moving. I thought it was steering setup at first but now the cars been on a setup system its all fine running 0 deg toe. it was then setup with 1 deg toe in, but this has made no difference to the handling.
Im running on smooth astro indoors with Schumacher Blocks Rear/ Cut staggers Front.
Any ideas before i strip it down.

Sean.