I put one on my ram with 5.7 hemi. Also had flow master muffler installed. It show around 1 to 1.5mpg increase. Not really sure if it was worth me money but I love the sound .
My wife has a 98 Z3 with the 2.8. Never had a problem, fast as hell (143 by GPS). I've offered to buy her another car and she won't even talk about getting rid of hers
Call Wayne Harris 404-925-9976. He lives just west of Griffin and has worked on several of my families vehicles. Very quick and very reasonable. Tell him Shawn Cain told you to call
buddy of mine here in Griffin had one with 12 inches of lift and 40 inch ground hawgs that he drove for years. If you know what your doing it's not going to matter.