so i have been having the weird random stall at idle issues (after i turn the truck on and try to roll out of the clutch, backing into a parking space, catching a yellow light and having to brake harder than normal, etc.) and did a vacuum check which revealed ~21 at idle. so i figured that's out.
did the "6 litre tune up", new water pump & hoses & thermostat, have previously done the PIP (twice because the first one was a dud), TPS, MAP, ECT, cleaned the throttle body and IAC, cleaned the EGR, and since the cats are hollowed i removed the smog pump and thermactor hoses. i plugged the lines and left the electrical connections like recommended to not get any codes, but though the CEL is off, i pulled a code 311.

so, anyways, i hooked up the scanner after finishing the water pump the other day and wanted to just do a basic tune, adjusting the timing, and making sure all's good. we got 4 codes:
1) cyl 8 <---- can't figure out what that means because the cylinder holds compression & gets spark
2) 311 thermactor inoperative (thought all should be good since the line is capped or am i missing something???)
3) 412 Cannot control rpm during KOER high RPM check
4) 538 Insufficient RPM change during KOER dynamic response test/ Operator error <---- code was repeated after clearing scanner memory and repeating the test with my friend doing the throttle "blip"

so if anyone has any guesses to what could be ailing me, please fire away. i'd love to clear them all from memory and have a wonderfully running truck without codes. as it stands, it's a wonderfully sometimes idle-stalling truck with hidden codes and no CEL. i appreciate any feedback!

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just in case i forgot: 1995 F250 302/5.0L 5 spd 124000 miles