How hard are you letting off of the gas, my experience from drivers schools and things that I have done is that if its a big lift and your pushing the car that its gonna be very unstable if not snap out of line on you. But if your just letting up a little bit (feathering the throtle off a little) you should pull right back into line without any incident. I dont know if its just this simple problem or if its the tires not being "broken in" as was suggested above. Definitly check out the control arms as xsperf suggests. Good luck and let us know when you find out what the issue is.