600SEL acceleration

[blk300E]

Need help trying to figure out why I do not have the pin you to your seat acceration in my 600sel. My 400E has it, my 400SEL has it, but the 600SEL does not. Acceleration in the 600 is not too slow but I'm not pinned to my seat (literally) as I do in the other cars mentioned. Also, I'm constantly reading about how the 600 gets to jail time speeds in no time.

An indy pull codes a week ago and the only thing that came up were bad mass air flow sensor, bad idle control valve, and battery voltage issues. MAF was replaced which corrected the hunting idle and possibly the code thrown from the idle control valve. Indy said that the battery voltage readings are not much of a concern.

What should I look @ next that would not cause a code to be thrown?