[Emjaydc]

I'm pretty sure OP is not going to reply to you guys.
The thread is from 2011 and his last activity is on 2014.

[German Straight-6]

Originally Posted by hassmaschine

2.5" is stock (the single section)

with any significant mods I'd be looking at 3".

if you are at stock power levels, is it best to stick to 2.5? what about 2.75?

[banshee28]

I am considering the Borla XS dual tips but I dont think it comes with the tips. That can add up to another $70-100. I like this one but yea I think at least 2.5" is better.

[CTinline-six]

Magnaflows are also a straight through muffler design. I doubt a 2.5" vs. 2.25" inlet on a Magnaflow is going to make a huge difference when you look at the flow over a stock muffler.

[German Straight-6]

Originally Posted by CTinline-six

Magnaflows are also a straight through muffler design. I doubt a 2.5" vs. 2.25" inlet on a Magnaflow is going to make a huge difference when you look at the flow over a stock muffler.

Is that a good or bad thing?

It sounds amazing when you get on the throttle, but some torque is lost in the low end and it doesn’t sound very refined until the engine is breathing freely. I gained more power throughout the whole rev range with the secondary delete VS. only the muffler alone

[hassmaschine]

Originally Posted by CTinline-six

Magnaflows are also a straight through muffler design. I doubt a 2.5" vs. 2.25" inlet on a Magnaflow is going to make a huge difference when you look at the flow over a stock muffler.

if 2.25" didn't make any difference then BMW would have put that on the car from the factory.

[CTinline-six]

Originally Posted by hassmaschine

if 2.25" didn't make any difference then BMW would have put that on the car from the factory.

There is a difference for 2.25" vs. 2.5" for the entire exhaust, yes. It would also make a difference for a muffler that is more restrictive like a stock one.

The magnaflow is straight through, and flows so well that the N52 does not make enough power for it to really be any difference between a 2.25" Magnaflow and a 2.5".