I got a 3" downpipe, 3" custom duals and 2 mufflers with 2.25" inlets and 4" tip. Am I hurting my POWER by having those two mufflers that are 2 1/4"? If I switched to TWO 3" inch inlet/outlet mufflers, would have give me MORE POWER?

 

im no turbo expert but i would say yes it is restricting from all of your other modifications. but i could be wrong

 

I have read that exhaust gasses flow on the surface of the pipe and when they hit an obstruction it will cause a pressure wave projecting back from the obstruction and really hamper flow of gasses ahead of obstruction. I have also read that restrictions further away from the engine affect power levels less, so mabye your mufflers aren't affecting power much. Well, anyway an optimal system has slightly expanding pipe diameter as it gets further from engine so that cooling exhaust gas expands along the increased surface area thus offsetting the fact it is becoming more dense and slower moving-referred to as "megaphone piping."

 

I'm thinking that this is exactly opposite. Basically, the fluid moves at the speed of whatever it borders. At the extremes (touching the pipe), the gas is damn near stopped, with the fastest gasses moving through the center. The change in diameter from larger to smaller would create a pressure drop at that area and increase the velocity through the area. I'm not sure overall how restrictive it is, but I can assume that it's "too little too late" in the exhaust system to make much of a difference. Sorry I can't really help, but I thought I'd at least try to offer what i know

 

the racing beat ones with the 3" system are only 2.125 so I think you're just fine.