Ok fellers.

So, this afternoon, I did the following things:
-Cleaned injector grounds on intake manifold
-Cleaned ground plate on left (driver's) side fenderwell
-Replaced old not quite dry thermal paste on the Power Stage heat sink
-Swapped a used Power stage in
-Double checked RSR wiring is actually intact at the terminals (The insulation is crumbling on this plug too, but I pulled them free and attached them, then put the plug on)
-backprobed the CPS and saw what looked like exactly the engine speed between the blue and red wire. No hiccups, no problems despite playing with the wiring
-Checked for and had voltage at the coil with the key in KP2


I used the component self-test mode to figure out that the wiring was loose to the RSR after I moved it and it was under some pressure. I reconnected each terminal individually and got it working again.

The fuse block for fuse #1 looks much worse than I expected it to - it looks pretty bad actually. I'm wondering if it's the whole problem.

It worries me that it won't run with the AMM unplugged, and I keep getting a "too rich/lean at idle" code when I'm nowhere near idle. In fact, the CEL usually comes on when I'm going 1500-2000rpm.

I tried to backprobe the O2 sensor and the CPS tonight, but I think the battery died in my meter because it was giving creative readings when connected to nothing.


Weird thing: I got a 3-1-2 code thrown at some point, and that's the knock sensor.
Does anybody have any suggestions? I can't afford to throw parts at it. It was running perfectly before I changed the heater core - and I either replaced the #1 fuse the same night or replaced it and drove with it fine for days without problems.