Pulling to one side on throttle can also be a sign of "tweak" - where the chassis is twisted. Check this by check (and re-set if necessary) the ride height and down-stops equally left/right and then lift the front with a thin screwdriver at the centre of the shock tower while looking at which wheel lifts off the ground first. They should leave the ground simultaneously. Repeat for the rear.
Alternative methods include a "tweak station" or 4 small electronic scales to measure the corner weights (which is how I do it).
If the chassis is tweaked, then firstly check that the anti-roll bars (ARB's) are flat (they can get twisted in a bad crash), while disconnected, loosen off all the top deck screws and give the car a "shake" to settle it, put it back on a flat surface and retighten the top deck screws, tightening across diagonals as you do it. [The setup book is also a good guide]. When you reconnect the ARB's, disconnect the springs and check that the left and right wishbones rise the same amount when lifting the other side.
HTH
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