Just a thought, but could his diff be messed up? It might be sending more torque to one of the wheels.

 

Always start with the easy and cheap stuff 1st.
It could be a differential problem, but this would be a very odd failure mode for a diff. I would expect to hear noise before seeing this symptom, couldn't hurt to change out the gear oil though, I do mine every 15K, and looking at the old stuff will give you good info on the state of the diff.

 

Got the S used from a dealer and I do have a warranty. No mods, 16K miles, and carfax was clean (if that really means anyting). It's a bit of a trek to the dealer though and I'm hoping to find a fix so I can just put this problem to bed without any more visits to the dealer.
Tires are the same make Potenza's and size with what seems to be similar miles on them (as much as one could tell by looking). I'll try the swap (temporarily of course).
Is this the type of differential with a clutch in it?? Could it be slipping causing too much power to be delivered to one side?

 

No, it's a Torsen unit so it doesn't make use of clutches.

 

For any of those who want closure to this thread - I wanted closure a long time ago... Finally after 4 or so trips to the not so local dealer, who I had to deal with in order to get me a free set of tires, the problem has BEEN RESOLVED. They're last resort correction (besides hard parts) was to replace the tires (and they ordered the wrong ones - what dealer doesn't have tires for current models in stock?) even though the tires had very low miles. NEW REARS - NO pulling! WOOOT!!

 

yep, definately tire pressure. I had the same issue... left rear was a few pounds lower... pumped it up to even them out, a day later, same story, pulled off the tire., turned out to be a massive nail causing a slow leak... i actually plugged it up and its "not bad" - awaiting replacement rubber shortly...