torque steer comes from much more than tirepressure. it can come from uneven camber, uneven castor, an excessively worn tire on one side, poorly sized wheels for the car(i.e. wrong offset), ruts in the road(not talking about bumpsteer). etc... in worse case scenario, a malfunctioning ATTS or poorly wired system(prelude SH).
Torque steer can also be caused by uneven springrates(for those of you numbnuts who cut your fuckin springs...) and a damaged damper. It can be fairly difficult to diagnose and in most cases you just have to live with it.
Bumpsteer is mostly caused by big wheels with stock sized backspacing and offset, but are wider than a stock wheel. for example, my accord. 43mm offset, 15x5.5 stock wheel. I don't remember the backspacing at the moment.
My Velox VX8 18x7.5" have the same backspacing and offset as my stock wheel, but it juts out 2 more inches than the stock 15. This is like a vector lever when you hit a rut or a bump with that extra 2 in. The suspension geometry of my passenger car having been lowered doesn't allow for that extra width comfortably. The bumpsteer can be reduced by properly aligning and bracing the front end(tower, tie, and sway bars), as well as stiffer bushings. But the bigger and wider the wheel, the more prone your car will be to bumpsteer.