I was a huge fan of the V10 M5, but after talking to a couple owners, I can't see paying $10K for a full exhaust system and getting the gains they did. When you're talking boost, I bet a tune alone will be worth at least 50hp and tq. Turbos are also more efficient than an N/A engine when driven right.

BMW knows what they are doing. I'm sure if the V10 was better than the new TTv8, this thread would have never happened.