E430 slow from 60-80
 

My 2001 E430 (Completely stock) averages 5.5 to 6 from 0-60 which I think is very good for the car. But, typically from 60 to 70 it takes at least another 1.5 and up to 2 more seconds and, from 60 to 80 is real slow, if I hit 60 at 6.05 I get to 80 in 9.92 or more!
Any ideas why I am out of power at that point. Is this to be expected with the engine?
I was thinking, the trans? it is kind of a lazy shift typically and if I manually shift it still takes a second or two to react and is not real solid. I haven’t been noticing but I suppose I may be in a "limbo" state between shifts at that speed. Or, I suppose I could be well past my peak HP band and losing power. If this is the case. How do I fix it so I don’t go so far beyond that point? I really haven’t been looking at the RPMS at that speed, Ill try to notice next time.

Any ideas? Besides that the power is ok for such a heavy car and I really surprise a lot of people with its speed.
I have only times my 1/4 once. It was 14.44 at 86 MPH. Wow if I could reduce that lag between 70-80 I could really get going. That 14.44 was not really the best it could do since the 0-60 was 6.1 and I have done much better than that.


Thanks for any help in advance