you're not getting responses because your question is insulting to those who choose to drive E38s. No offense intended- I'm being straightforward.
Answering your question objectively is nearly impossible. Acceleration is subjective. You may be asking too much of a very heavy car, despite its near 300 ft/lbs of torque. That said, a hot rod trans am driver (Wr6 or whatever) was once shamed when he thought he would run off and leave me.
Your symptom is too vague.
It's not what you buy, it's what you build- Unknown
EN90283 - Stabled for HG repair
DH06247 - Running like a champ