Originally Posted by ianf
Thanks for feedback. Before and after dyno would be good if you go back to stock. I see ESS claims 350RWHP (25RWHP increase) as per their dyno chart. Joe's car does 350 just with mid pipes!
Cobb claims 14HP extra.
All these claims are sus, and you can't really just read dyno figures. I would have gone with Cobb if it was out when I bought the ESS as I like the data logging features.
Looking at custom tune options however though once everything is in. I have a friend who's just done a custom tune on his 335i by a guy who normally work on Porsche Race Cars so will investigate further once I sorted out my bolt ons.