I had a pacesetter cat back on my '91 celica. It was OK at first but became VERY loud after about a year. I think something comes loose in the mufflers. I would go with something else if I were you.
On my '80 longbox I wanted it to be free flowing and louder so I just welded a thrush glass pack in place of the stock muffler. It's cheesy old school I know but it kind of matches the personality of the truck and it felt like it freed up a little backpreasure over the ancient stock muffler. I'm getting 20+ mpg even with stock gears and 33s. The truck allready had a decent header so that helps I'm sure.
I don't think you really need the 2 1/4" on a stock carb 4 banger but if you are starting from scratch with new exhaust you might as well go bigger than the stock 1 5/8" or whatever it is.
