2002 3.8L (not Super Charged) Stalling Problem

I have a 2002 Bonneville with a 3.8 that will not stay running (unless I keep a foot on the accelerator. It started with a "chugging" when I would start out (cold or hot engine temp). I pulled the EGR valve and inspected it (looking for a gummed up valve). The valve looked good but the gasket looked a little jacked up so I bought a new one. After that, the car started to stall at intersections or town/city driving. It finally set a code (P0102). All of the tests were performed leading the problem to be a MAF sensor. I replaced the MAF sensor but still have the same problem. (I will be honest, I didn't buy a brand new one because I didn't want to throw the money away if the problem was something else). I have actually put two sensors on but neither changed the way the car acted. I need some technical help PLEASE.

Check the MAF screen for debris.
Check for vacuum leaks.
Check the PCV valve & O ring(s?)

I have checked for vacuum leaks but I will be sure to check the screen for debris and the PCV valve o-rings. Thanks for the quick reply!

Okay, I checked for vacuum leaks (using ether), no sign of leaks, I checked the PCV valve, looked clean and not gummed up. O-Rings looked good. I was wondering though, does the MAP sensor have three exposed (flat) metal tabs on the bottom? I looked at an example on NAPA and it seems to be the same thickness but one thing that does look different is there is an orange nipple smack dab on top of the picture in the NAPA web site and mine doesn't have such a thing. Mine just kind of clips into two clips on either side. Sorry if I sound like a novice mechanic (could be that I am or maybe don't qualify as a mechanic at all). Thanks for any help anyone chooses to offer.

The map sensor should have a sealing " nipple" where it fits down into the fitting. BTW 102 can be caused by any air entering the engine unmetered, double check all the o rings for the map and pcv.

All who responded, thanks for your assistance. I purchased a new MAP sensor and just like that, the car runs like it should. Now that that problem is solved, what could cause a slight chugging when you start out (like backing out of a drive way)?