Question for a BMW tech.

[Rocknpalms]

I have a 2004 325i that I have brought in for every scheduled maintance since I owned it which was at 21k miles. The car now has 52k and factory warranty ran out at 50k. I now have a hesitation between 2300-2500 rpm at 70mph high gear with slight acceleration. I do not think it is fuel filter or injector delivery as it has plenty of fuel under hard acceleration at a much higher load and speed. I dont think it is ignition because it is ONLY at the above mentioned conditions. I was told it is possibly the air flow sensor starting to go bad. If this is the case can it be cleaned or does it need to be replaced? Also I have no check engine lights that come on.
I also use mid grade fuel and not premium fuel most of the time at a AM PM.
I will be filling up with premium from the major brands the next few tanks to see if it changes.
Please advise.
Thanks

[Invisible Sun]

I'm thinking air mass meter (cannot be cleaned), but it seems strange that it only happens at that speed. It almost sounds like a load caused issue that might be ignition related. If you hold it at that failure point long enough it will probably set a fault in the DME. All BMW's require high grade fuel, so it may be a contamination issue (water, poor octane rating). Don't want to get too technical here, but you might need to pony up for some diag on it.

[bigq]

Sounds like the ignition problem since it is under load. Like it has been said bad fuel could be an issue also since the computer would compensate and retard the motor for safety. not that it would be bad, but performance will be impacted. If a problem exist it should pop a light I know our did whenever there was an issue.