What size muffler for custom setup? (magnaflow, dynomax, borla)

[Nimble]

I know the muffler should be 2.25" inlet/outlet, offset holes right? And also oval vs round.

My question is does it matter if the case is 5"x8" or 4"x9"?
Also the case length, they start as short as 11" and go all the way up to 20 or so inches. What have you guys gone with? Also, do you keep the factory strap muffler hangers? If not, what did you use? Thanks and any pics would be appreciated of your set-up.

EDIT: this is for a 318is.

[Sean]

Just wanting to bump this.

I could probably get a 5x8 to fit, right? I'm going to look into a custom way to mount it. The problem I'm running into now with ym stock exhaust is it keeps hitting my rear valance on hard left turns. It wiggles A LOT! I want my exhaust to stay put if I have a nice muffler there! :D

[volgapower]

i wonder what diameter should me the exhaust pipe on 318i??? whats the stock diameter and whats is the recomended custom one?

[///Motorsport]

I have 2.25 I think on mine, but the PO had it welded on in a shady way, at an off angle, etc.. Pretty sure its stock/oem replacement stuff though.

Im going with a cat delete, resonator delete and still trying to figure out which muffler. I was going to keep the muffler that's on there, but it won't sound that great with new straight pipes.

Any suggestions? This is on a 318is as well. I wanted to stay away from chrome if could, wanted one tip, and made in germany if possible.

But The dynomax and magnaflow might be the best for on the cheap.

So one tip or two on a m42 muffler? Think one keeps it legit, but two is always nice too. Is one of our choices around $200 or so lighter than the rest?
Any other thoughts?

[Tree18is]

my problem for the "wiggly" exhuast, when i made the exuast hanger i used that small gauge re-bar.....never mind this is half ass, just be glad i did it to my RX-7.
end result, you can stand on my muffler...and jump the car, off road it and not fold the muffler under the back right tire (done it)
so thats how i fixed my problem, dont let the shop scam you, make sure its straight and SOLID! i see to many lost fuckers with cock-eyed exhuast and stuff that wiggles when they accelrate... its sad, but at least i get my laugs.
my two cents, good luck.