BMW 4.6 is poor acceleration and hesitation

[Aman]

Hi I have a 2003 4.6is
When I first owned it, a year ago, everything was fine and it was very fast
Recently the EML came on and the power seemed to gradually disappear
All 8 spark plugs were changed and 3 bad coils were diagnosed and these were changed
Now the car idles very smooth, but when I try to accelerate it is very slow/hesitant
I can overtaken by a 1.4 vw golf!
The car can't go above 4000rpm (it struggles to get there)
At approx 4000 with pedal fully depressed I start to hear a rattling from engine area
Occasionally I feel the full power of the car trying to come through, but not often now
Any ideas? Your help would be really appreciated