Well, I did the standard tune up (plugs, wires, cap and rotor, all AC Delco) and found 3 plugs with some pretty heavy deposits. Fired it up and it ran about the same, very spongy, no power.
I removed the upper intake tuning valve and saw some fuel puddling in the plenum, I thought "Great, it's the fuel pressure regulator, problem diagnosed." I opted for a complete replacement unit rather than just the regulator. Long story short on that, $300 less in my wallet and my problem was still there.
I made what I consider to be a great investment, a $35 factory manual set from Ebay. It's comical to stack the factory manual next to the Chilton. About 3 times as thick, thinner pages and smaller print to boot. I don't think I'll ever buy a Chilton for one of my vehicles again.
Anyway, after reading the diagnostic flowchart for my vehicle symptoms I decided to take a look at the exhaust system. I started by measuring engine vacuum at the manifold. At idle it was pulling about 15 inches of vacuum, at a steady 2500 RPM it was almost zero, indicating a possible exhaust restriction.
I then drilled a 3/16 hole immediately before the converter and used a fuel pump/vacuum gauge to measure exhaust backpressure. I was getting about 1.5 psi at idle (manual says no more than 1.25) and 7.5 psi at 2000 RPMS (manual says no more than 3). I then drilled another 3/16 hole immediately after the converter and welded the first hole shut. Less than 1 psi after the converter. I'm going to try a straight pipe in place of the converter sometime this week. If all goes well I'll throw a new converter in and hopefully be on my way! I'll let you all know how it goes.

 

Sounds like you found your problem.

 

So I've been snooping around the forum for advice on whether or not to buy a direct fit or universal catalytic converter, and I've heard a few folks condemning the magnaflow universal. This was the one that I had planned on picking up, as I have the time and a welder to make everything fit. I'm wondering if the reason people are giving these a bad review, is the fact that they are simply replacing the converter without correcting the problem that caused it to fail in the first place. As I understand it, these things don't just decide to plug up on their own, there is usually some other issue with the vehicle that causes them to fail. Any thoughts?

 

Replaced the converter with a Magnflow universal. Ran like a champ for the first day. On the way home from work the next day, it started idling like crap but would run fine while in motion. Took a good look at the factory manual this Sunday and found that the EGR valve was stuck in the open position due to a chunk of carbon. I'm pretty sure I dislodged this chunk of carbon when I was messing around in the upper intake manifold. I made the mistake of not cleaning the passages and valve while I had the upper plenum off. The valve and passages are a lot easier to get to with the plenum off. I was also finally able to retrieve trouble codes with the scanner that Oreilly's had. It was an Autoxray Codescout 2500. The scan tool that I was using before was the Innovia 3100,doesn't seem to work on my particular vehicle. Thanks for the help guys!