Let's see. You're upping your tires. You've readjusted your seat. She moves to the left and your having issues in turns. Your issues are not all related to the steering or tires. Sounds to me like you've got issues with the trans. Something is out of whack back there. You can run them sticks all the way forward and she's still creeping, she's off. So get it in the shop and have the mechs tear into it and reset everything.