Also, check VREF at the MAF/BP and the EVP sensors. Could be a bad EEC or a shorted wire.
Yank the connectors off the sensors and see if there is +5V VREF. If not, you'll need to go to the EEC, yank off the main connector, see if it's shorted to ground, make SURE that the wire you're testing is the same wire as the VREF to the sensors. If there isn't any short to ground, then it's a bad EEC.
Alright, well I checked VREF at MAP, EGR and TPS sensors and it's 0 at all of them...all sensors connected, so no bad ones to mess it up. I then checked resistance between black TPS wire and Battery with (+) cable removed and it came back as "infinate," so I guess that's bad? I'm gonna go read about resistance tonight and i'll double check it again tomorrow because it was dark tonight. I'll also find the 10 pin that carries VREF and test that. Thanks for all of the help guys.
I had this happen as well on my own car. Jrichker's advice is right on. My problem ended up being that the orange/white wire splits into two wires one feeds the TPS the other feeds the EVP sensor. Mine didn't seem to have ever had any insulation where the two wires split at and had corrodded until the one for the TPS fell off. A few minutes with a soldering iron and some heat shrink and I was back in buisness. not saying this is definently your problem , but it would be a good area to look at. Just follow the orange/white wire down from the EVP sensor and you will see what I mean.
I guess a bad connection at the CPU will do it! Went out to test resistance of VREF wire at CPU Connector to TPS and decided to put the CPU connector back on and tighten the bolt just to see if it was a bad connection...VREF=5.02! I kinda feel like a jackass, but at least it runs. It starts, but it doesn't have headers now, so I can't actually drive it. I'll get the headers back on and hopefully kinks worked out this week and have it on the road this weekend or next week. I'm excited! This makes my freaking year!