Quote:
Originally Posted by justinnum1
Question for you guys that own the performance exhaust or have heard it in person...
Does the left muffler stay close with the flap till 4000rpm like the stock exhaust?
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No, there is no flap in the M Performance exhaust. The main differences that give it its louder sound are the lack of this flap (meaning it's "open" all the time) and the fact that the muffler itself is made of a single layer of metal instead of two layers (so you also save a couple pounds).
If I had to choose between HK (a must-have if you ask me) and the exhaust, I would get HK and simply unplug the exhaust valve. I've had my valve unplugged for 35,000 miles now and love it every single day I drive my car, sounds very close to the Performance exhaust with zero ill effects. I've even asked a couple of my friends who are BMW techs and all of them assure me there are no draw backs to doing this. There are a number of ways people "golf tee" their exhausts, but the best way is to go into the trunk and simply unplug the connector so the valve stays open all the time. Search for a DIY guide on this site.
EDIT: Woops, I was talking about my 135i and forgot which forum I was on. Lucky for you my brother has an F30 328i and we unplugged his exhaust flap to test it but there was literally no change in the sound that you could notice so don't bother doing that.