When I floor my 99 E55 from standstill the throttle doesnt really response as it should. Above 2000 rpm it works as it should with great acceleration.

I have also noticed something else which I think has got something to do with the poor acceleration.

If I have the motor running in P or N and gently rev the engine up to about 1200 rpm and hold the accelerator in that position, the engine will go back to about 700 rpm. If I rev the engine to about 1800 rpm and hold the accelerator in that position it also will go back to 700 rpm. It is the same all the way up to 2000 rpm. But when I rev it to over 2000 rpm, lets say 2200 rpm, and hold the accelerator in that position the engine stays in 2200 rpm. I cant figure out why the engine is dropping rpm in the lower sections, and not in the higher sections.

This is why I think the throttle response is poor under 2000 rpm. MB doesnt get any error codes in their diagnose computer. They replaced the MAF with a new one but nothing happend. They changed the spark plugs and the gasoline filter and that made the car go a little bit better, but the problem is still there.

I've been thinking about the ECU, but how can you see if there is something wrong with the ECU? The dealer says there are no error codes, and I won't pay for a new ECU if I'm not sure that is the problem. A new ECU is a lot of money!

Someone said it could be the TPS combined with a bad MAF. I don't speak very good english so I don't know what TPS means. What is it?

Anyone heard of this problem?

Marky