I used to live in Oregon with miles and miles of interstate at my disposal. I used to race my car on circuit courses. I say used to because I took my stock 93 honda accord to the track one day and whupped everyone in my class and got hooked.
I went ebay crazy...I bought lowering springs. I bought smaller rims and tires to lower it more. I bought front and rear strut tower braces. I bought this exhaust. Honda Accord 90-93 2/4Dr 4" N1 Muffler Catback Exhaust 2.5 inch piping. And a lot of more parts that are irrelevant to this post.
Now I live in Vermont. On a quiet country road with rolling hills and no interstate. I got sick of the 4" exhaust tip (not muffler), so I cut it off and clamped on a thrush muffler that was supposed to be quieter than the can. I find it equally as annoying.......
I decided to go back to stock with the tailpipe assembly (axle-back) with an actual muffler. My dad got it from NAPA for me for my birthday today. All excited like its Christmas Eve, I jack the rear of the car up...get wrenches ready............
Right, 1 3/4" tailpipe assembly! Cant find one online anywhere for a 2 1/2" exhaust. I just want some peace and quiet in my car and for my neighbors!! Somebody please tell me if I can find this tailpipe assy. in the size I am looking for, recommend a quiet muffler or tell me not to worry...bolt the smaller tailpipe on and it will be fine. I doubt that, but I am at wits end. Thanks!!

 

why don’t you just take your OEM muffler to a exhaust shop and have them fab. it up for you? You can still keep you bigger piping and they will use a reducer piece from your sized exhaust to the OEM muffler.

 

whew, let me tell you form personal experience that if you have aftermarket pipes form the manifold back and then reduce it to the size of the stock muffler, you will have performance on the level of a stock vehicle again, the size of the pipes will restrict flow no matter if the rest of the system is bigger, better to go with a muffler that is known to be quiet, thrush are known to be loud, like on trucks, magnaflow and apexi n1 series have a low rumble, but there is not a aftermarket system out there that will give you better performance without it being louder. just take some time and do some research

 

he is running a 2.5' pie that’s too big for f series engines. Unless it's a fully built engine.
So using the OEM muffler will help create some of the backpressure he needs.

 

oh yeah, umm, my magnaflow is on my mr2, I had an aftermarket one on my accord, but sounded bad, too big piping, like you said