TDI Acceleration Problem

A few months ago I suddenly lost acceleration power in my 2000 TDI Jetta. Now, I have little acceleration power. And, if my AC is on, I typically cannot get above 60 mph, without turning it off until I reach over 60mph and then turning it on. It seems to me as though it is not shifting properly...if I have the AC on, my RPM's go very high and I don't get any added speed. Anybody have any idea?

Thanks!

If you're getting an abnormally high amount of black smoke, suspect the turbo. Otherwise, suspect the mass air flow sensor (MAF) - very common to go bad. I think I saw somewhere VW extended the warranty on it to 70K miles if that helps. Here's more info:

http://users.vnet.net/w123d/w123d/vw/repair/mafrig.htm
http://www.tdiclub.com/TDIFAQ/TDiFAQ-7.html
http://tech.bentleypublishers.com/thread.jspa?threadID=6255&tstart=30