It's going to be tough getting Toyota to cover it...it's 4 years old, and at that age, some things start to wear out. You could need an alignment, you could have unevenly worn tires, you could have mismatched tires, you could have a suspension problem, you could have a slightly bent rim, you could have a car that's been in an accident...etc., etc. I'm not saying you have any of those issues, I'm just saying that those are all potential problems that might have to be proven to be NOT the issue before it would be covered. Is it an extreme left pull, or something subtle?
That being said, if there is a TSB, you've got a chance for at least a little help. TSBs usually only cover the car when it's under warranty, but there's a slight chance of free parts from Toyota corporate outside of the warranty period. How many miles are on the car? What is the in-service date? If it's less than 36,000 miles and has an in-service date later than November of 2005, you're still under warranty. Can you prove a good service history done at a Toyota dealer? Toyota is much more likely to pay for repairs outside of warranty if you can prove you've properly maintained the car at a Toyota dealership.