I had the same problem after installing the K&N filter in my 2001 base... Really cleaned the MAF (almost used a whole can of MAF cleaner) and put it back in and no more problems...has run great since cleaning the MAF..
So I took a look in the throttle body and it looks clean so I'm going to give changing it a miss unless I have to. It looks really fiddly to get off and on and I don't want to break more stuff.
I filled up with a fresh tank of premium and threw in a can of injector cleaner, and she runs better.
I disconnected the MAF sensor and it runs fine in limp mode.
So think you are all right and the MAF sensor is the logical next step. It's on order, will update tomorrow. Thanks!