I love my 128i with DISA intake, AA headers, and MILV's - but it was too loud after the headers were added. I'm a broadcast sound mixer and have to protect my hearing. The shop that installed the headers said the car would be "slightly louder than stock". In reality it was twice as loud. I think a lot of mechanics and gear heads have hearing loss, BTW..... So they don't have an accurate concept of how much louder a mod will because it doesn't seem loud to them.
Interior noise levels were in the 80+ dB range (windows up - open windows even louder) after the headers were installed. Way too loud for me. I had to have a 1/4 wave Helmholtz resonator fabricated to reduce low frequency drone at 125Hz plus 2 Car Chemistry 2 1/4" baffles mounted just after the headers to reduce overall sound levels.
Cost me about 10hp10Tq but my ears are much happier. The car's exhaust still sounds glorious with windows up or down, but volume is livable to me and less intrusive to others - about 73dB at its loudest. The photogs still hear me coming when I'm a few corners away at Tail of the Dragon...
Corrected dyno results are 288HP and 273TQ with DISA, AA header, MILV's, and the CC inserts. (The 1/4 wave Helmholtz pipe doesn't have any effect on power).
Sound Samples:
https://www.dropbox.com/scl/fi/m5phf...serts-001.WAV?
rlkey=5vgasn7vx1aip3mc9dn2j99za&dl=0
https://www.dropbox.com/scl/fi/2xaj7...sxw5nl3pe&dl=0
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'11 BMW 128i 6MT
Titanium Silver, Sport Package, Cold Weather Package, Sunroof, Sensatec
DISA Intake, AA Header, MILV's, Stage FP Tune, VAC Motorsports Quaife LSD, CDV Delete, M3 Upper and Lower Front Control Arms, Powerflex Yellow RSFB’s, "Square" Tire/Wheel Set Up: Michelin PS A/S 3 225/45 17"'s on 17"x7.5" Type 262's