Happy I just did this, very noticeable difference. Did it the exact way the OP suggested. When coasting, I can't really hear a difference but the second I get on the throttle you know. Also, the instant I started my car after doing the mod instantly put the biggest smile on my face.
Took about two minutes to do. Tops.
2011 N55 135i | Wagner Tuning Highflow DP | AA Signature Exhaust | JB4 Stage 2 | LCI Tails | ER CP