ok guys i have an m30 afm i want to know which is better stock box modded with the m30 afm which ive done before and don't mind doing again or a cone filter with heat shield? which is better?
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GRM has done this test with multiple cars. Most cars gain 1-2 hp top end, but lose 3-4 lb/ft down low.
I remember on the Honda Civic that was done recently the PO had removed the intake snorkel for a better tone. Just adding that piece back on to the stock filter box netted 3 lb/ft.
Filter boxes are tricky. I'm fairly sure that BMW's factory box is better than any cone filter, but thats just my opinion.
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