hi,
what do you guys think about that?
http://cgi.ebay.com/ebaymotors/MAF-SENSOR-MASS-AIR-FLOW-VOLVO-740-240-760-940-850-007_W0QQcmdZViewItemQQcategoryZ33557QQihZ002QQitem Z120063991248QQrdZ1QQsspagenameZWDVW

Spend your $2.99 on a can of CRC MAF cleaner. If that doesn't do it, and you're getting a code for a bad MAF - time to go buy another one...

Not sure what this guy would have you do, but it looks like BS to me. Do the E39's have a wire or film MAF element? Most MAFs have a burn-off cycle to clean the element - wire one's generally last longer. From what I've seen MAF cleaner is fairly ineffective, and that it's the cycling of the burn-off element that leads to the eventual failure, and the cleaner doesn't really add anything to the inherent ability of the MAF to self-clean. A good rebuild shouldn't be that expensive.

Near as I can tell from the negative feedback responses, he has you soak the thing in denatured alcohol for 3 minutes. Probably about as effective as MAF cleaner, which did absolutely zero for mine when I did it. A few guys have reported some tangible results.

A friend of mine did some logging of air mass flow before and after cleaning his MAF in a 1.8T engine. The improvement after cleaning was very minor. Only a replacement with a brand new MAF made a noticeable difference.