I know that this subject have been up more than a hundred times, but is there any sure way of telling if your MAF is dead? What kind of monitor would tell you that? Mine is only four weeks old, and I don't wan't to throw it away if it's not the one causing problems. No Check Engine light or anything, fine idle also after reset, but does'nt pull away stable, and running with 2500-4000 RPM with half throttle is almost impossible :-(

 

Do an ECU check and look for error code 23 which is the MAF.
simply locate the two BLack connectors under the drivers side, connect and turn ignition on without turning the engine on.
You'll see the check engine light flash, if it is a constant 0.5 second flash then no faults detected, if a fault eg the MAF it will complete 2x1.3 second flash and 3 shorter flashes=23.

 

If the ECU detects an error, would'nt the Check Engine light then start flashing?

 

"Fine idle also after reset" - that's usually a pretty good indicator - if it's OK after a reset (ie unlearned what it has learned, as yoda says ) then it's getting ok info. Probably.

"but does'nt pull away stable, and running with 2500-4000 RPM with half throttle is almost impossible" - was it cold at this point? They are all pants until the lambda sensor is warm, which can take a while. If it's when it's warm, it could be something else...