Agree with Mulchman. Chek to see when a full tune-up was done on the car. Also feeling vibrations at low RPMs could be a bad engine/tranny mount as well. Congartulations on the car, you will enjoy it. The 6 is a nice ride . Post a few pics of her as well.
2008 650 Convertible- 6 Speed manual- Sport package- HUD- Lane Departure- Comfort Access- Merino Leather- HD Radio- SAT