It takes air for the engine to run, so the throttle is open, or you've got a big hole open somewhere, like a PCV return hole or something like that.
An engine can't run 6000 rpm just due to sensors or any kind of computer mistake, unless the computer can control the throttle directly. It needs air and fuel to run that fast.
^^This. My first though was where is the engine getting enough air to do this?
I had seriously thought that the throttle was stuck open somehow. It moves back and forth freely (as in not stuck open lol), though, so how the HELL is the engine getting enough air to rev to WOT?
The computer has no direct control over the throttle. I only have a TPS, IAC, and MAF. I had unplugged each one individually and tested the RPMs. The only one that made a difference was the MAF sensor.
Upon unplugging, it was difficult to start, then idled almost perfectly for about 3 seconds before acting like WOT again. Then, however, it idled perfectly, WOT, idle, WOT... you get the picture.
Also, the MAF is cracked and I can see the leads inside the plastic housing. I'll find another and replace it, but I don't think that's the issue.
As for a big hole somewhere... I'm at a loss.
Again, all I did was solder on a new ICM harness connector. Nothing has been the same since.
I did not, however, disconnect the battery while doing that. Is it possible I've fried the PCM somehow?
Keep the replies coming. They do help!