The part number for just the sensor part of the MAF was posted on the i-club. Revision got and installed one on his 99RS. It seems to be working. I'm in the process of verifying that it is the proper PN for the 99, but as far as I can tell it is. And at around 50 bucks it's a lot cheaper than getting the whole MAF. Details here
http://www.scoobymods.com/forums/showthread.php?s=&postid=887#post887
http://www.scoobymods.com/forums/showthread.php?s=&postid=887#post887