Alright, first a little history on my 1999 Blazer 4WD.

When I first bought it, the previous owner had decided to upgrade the air filter to one of the giant conical types. In the process, he also removed the MAF sensor and capped off the small air hose (the one normally attached to the larger air conduit) with another small filter. The Blazer had a constant code showing an issue with the MAF sensor, but otherwise ran alright.

Since then I decided to try and improve my fuel economy by returning everything back to normal. I picked up a factory air box, installed a brand new air filter, installed a MAF sensor, and returned the air piping to the factory setup. I also installed new plugs, wires, rotor, and a distributor cap. Shortly after, I started having trouble with the engine missing at take-off during rainy or humid weather. I checked all the plugs and replaced them with yet another set (AC Delco) with absolutely no change.

My check engine light went away for a while, then came back with a code identifying the bank 1, sensor 1 O2 sensor. I recently changed that and the code went away, only to come up about two weeks later with another code identifying an issue with the O2 sensor past the catalytic converter. My converter's heat shield is the spot-welded type, and it recently started rattling like crazy. I installed some metal strapping around it to hold the shield still and stop the rattle. My theory is that perhaps the spot welds are designed to let go when the catalytic converter gets too hot so that the rattle will alert you that its time to change it, but I find it a lot more likely that I'm talking out of my ***.

Two weeks ago, I went on an hour-long round trip drive down the interstate, and as soon as I got back in town it started dying. I was showing a quarter of a tank of gas and have never had an issue with the fuel gauge. However, at one point I noticed that every time it restarted, the fuel gauge would be all over the place (typically indicating half a tank). Did I run out of gas with a faulty level sensor, or could it be related to the other problems? After refilling the fuel tank it stopped trying to die on me, so the obvious answer would seem to be that it was simply out of gas. However, could that mean the fuel pump could be at fault for all my other issues as well?

I really don't know what to check next or how to check it. Could it be a fuel pressure issue? Where (please with a picture) is the fuel pressure test point? Since I don't know how to weld, how do I check my catalytic converter without chopping it off? How many different sensors will I need to check and clean?

As my topic title states, I don't even know where to start diagnosing it. I was making plans to take my wife somewhere for our anniversary at the end of next month, but at the rate its going I may need to cancel. I'm about ready to push this thing off a cliff; I would trade it in if I had the credit to finance a new car. If anyone can help me with any tips to get this hunk of junk running right again, I would HIGHLY appreciate it!

EDIT: Also I would like to mention that my fuel economy has went to hell after this fiasco.

Here's a couple more head-scratchers to throw in the mix.

My A/C system has a leak, but when I charge it up it blows cold for about two weeks before running empty again. However, the completely strange part is that whenever its charged up, regardless of if I'm actually running the A/C, the engine bogs WAAAY down at take-off. I mean, foot to the floor and I could push it up the road faster. After the refrigerant has all leaked out, it has all its power back.

In relation to the rough running at take-off, it seems to take off a bit smoother when I run it without overdrive. You can still kind of hear it missing while running down the road, but it doesn't have as much effect on how it drives.