I would recheck your alignment, it sounds like you have either very little or negative caster or too much toe out. Which subframe do you have? If you have the Samberg one it may be possible to get negative caster, or at the very least very very little. I didn't check to see what minimum caster angles were but I'm close to centered with ~4.5 degrees and it's a big cam.
If you had something that loose I'm assuming either you or someone else would have caught it while checking out the car, I've never seen a "broken" rack feel overboosted, tight, binding, "crunchy" are all possibilities but I have a hard time believing overboosted, especially if it still does it with the PS disconnected. Get us the alignment numbers before you start spending any more money.