Originally Posted by TheSt|G
Not everyone loves turbo lag.
Have you ever driven a 135i or 335i? That's a very interesting comment to read for anyone who has.
The elephant is the room is that centrifugal superchargers add mostly just peak power as boost raises exponentially towards redline. Little to no added low end, low to moderate midrange gains, then the biggest gains right at redline. A blower (Eaton or Whipple) would add power across the board.
A much better option is to trade your 128i in on a 135i. 250whp+ bone stock with significantly better low end and midrange. Then slap a tune on it and it's not even close. The only reason to keep your 128i and put a supercharger on it is personal attachment. It's not a financial or performance decision.
This is a neat kit, but it is a hammer to drive a nail that doesn't exist.
2009 BMW 135i, 6 MT, M Sport, DIY DCI, Cobb AP, Apex 18x8.5+9.5, 235/265 Starspecs