I have decided to go with the SI/SO magnaflow muffler and af1 intake. The ? is about inlet & outlet size. Stock pipe is 2.5" in and out. Would it make any difference to go with 3" pipe or just cost more money with the same outcome? And would sound level be close to same. Thinking of the 5x11x22 muffler.

 

the .50 in makes no diff in a dyno test

 

Even if the 3" pipe doesn't make a dyno difference, it will increase the efficiency of the engine. You do need some backpressure to effectively scavenge all of the spent fuel/air mixture and combustion products during the exhaust cycle, but too much limits the engine's potential. 3" isn't too drastic and your engine should exhale a little better. You might even see your mpg's go up a bit. Plus you've widened the exit to take advantage of anything else you may install down the line for performance.

Hope this helped a little.