My car does exactly the same thing. Its pretty annouying. Same as you tranny shifts smooth as silk. But if im coasting down the road foot off the gas the rpms will go up and down slightly. Can't figure it out.
2005 BMW 745 LI Sapphire Black
22's, AC Schnitzer Kit, H&R Lowering Springs, Tinted tails and Signals, AC Schnitzer
Carbon Door Pillars, Cross Drilled and Slotted Rotors, Tuner Mod, Tinted Windshield,
30% Tint all the way around, and some other stuff I forgot.