If you have a 2001 then you have the e-gas and not the wire throttle.
There are several revisions of the MAF for e-gas, and if you had a 2000 there would be a chance that you had the earlier one. For 2001, you have the most recent revision. This article from Pelican Parts 101 Projects for your Boxster has a breakdown and also a link to order the correct one.
If you determine that you need to replace your MAF, then this article will help you to figure out the correct one.
Steve
Thank you Steve, just the info I was looking for. My car just hit 36k miles, so I will get a new MAF sensor and see what happens. Maybe change the O2 sensors later as these are all fairly easy to do myself.