I just installed the Meisterschaft exhaust GTC-EV 4x90mm for my 328i over the weekend and have been absolutely loving it.
However, it was not all that rosy when the pipes came. The bracket hook on the section 1 AR pipe was welded on the wrong side, so my mechanics had to saw it off and reweld on the correct side of the pipe.
Baring that incident, the sound it produces is phenomenal. In closed mode, it feels about 50% louder than the OEM exhaust if you stand right beside the pipes but if you're in the car you won't hear much of a difference at all.
Open mode is where it's at. Feels very bassy and gives off a loud 'fart' when you shift gears.
Butt-dyno tells me there is at least a good 8whp increase from 2.5k rpm to red line. Maybe a bit of torque is lost in the low rev range. I will try to dyno one of these days to confirm my suspicions.
A little video I pieced together with my in-car camera audio, which really doesn't do justice to the sound (because it is much louder in real life and the mic sucks), but I hope you get the idea of the sound you will hear in the cockpit
