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      02-01-2013, 11:49 AM   #6
foghat
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Drives: 2008 135i
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Quote:
Originally Posted by gmane View Post
And on a different note they also say that a axel back muffler upgrade is required? Now we all know from various threads that an axel back system shows minimal gains if any because the bottle neck is way up the exhaust line. That said if you're really pushing some boost then more boost = more fuel = more exhaust therefore we need better airflow but you'd think that they would recommend going to a minimum of a 3" piping and not recommending just an upgraded axle back?? Anyone care to chime in on this one? Sorry for the thread jacking but it's sorta relevant?
According to what I see on their site, for stage 2 they recommend a cat back exhaust, not axle back. And of course downpipes are required. between the dp's and cat back your are getting rid of all the cats. Which, of course, will improve exhaust flow.