I've got a Thorley tri-y header,2 1/4 tubing,high flow cat and 2 1/4 Flowmaster and I love it. Sounds great and tach's up a little quicker than stock.

Like DRM said anything over 2" won't gain performance on a Toyota motor. I tried 2 1/2" and sound wise it was great but there was not enough backpressure. I feel 2 1/4" gives a little more back pressure and a little better sound. I've tried 2",2 1/4" and 2 1/2" and I think 2 1/4" works and sounds the best. With 2 1/4" I didn't notice any gain or loss,power wise, over the 2" but it's got a little deeper tone to it.