First of all make sure the chassis isn't "physically" tweaked - check that the chassis will sit flat on a flat surface, and won't rock around.
Second, set your ride height with the shock collars even on both shocks.
Third, check your tweak, and make any adjustments to the shock collars to even the "suspension" tweak out.
Fourth, re-check your ride height, moving both shock collars by the same amount if you need to change it.
Car should now run straight on the track, on- and off-power, and corner evenly left and right.