One thing I've done before is an octane booster, just something you can pick up at your favorite place to get additives and such. That's what I've used, but I have a 4-banger so I saw more than you would see from probably a 6 or 8 cylinder. Also, if you do an oil change, you could do some anti-sludge oil, that might help.
Actual parts, I'm not too sure as I haven't gotten there with my car yet. Hopefully this cheap alternative answer helps a bit.