Been researching forums, including this one, but haven't found my answer(s) yet for some diagnostic codes, figured I'd try asking..

Long back story to try to give all details:
1995 F-150, 5.8, E4OD, 3.55LS, 4x4, 64k original miles (mostly hard miles)

It was used as a snow plow truck and for weekend work in Upstate NY until around 2000 when it came to Western NC then pretty much sat other than an occasional short drive until I got it from the original owner, a family friend, in 2009 with 42k miles.

I used it as a work/farm truck and honestly abused it more often than I should (loaded it like a rail car and drove it like a race car), also occasionally plowed snow in our mild NC winters, until I blew a head gasket in summer 2015 and it sat until this March.

I tore everything down and put back together with no surprises until I found the air pump had seized so I removed all of the thermactor equipment other than the catalytic converter and the TAD and TAB solenoids are hooked up electrically, not to vacuum. EGR and vapor canister are still intact and hooked up also.
I replaced every vacuum line and have checked routing and connections numerous times, the vacuum reservoir is also still hooked up and does not leak.

Truck starts, runs, and drives great with or without the check engine light discussed below.

Now the codes:
KOEO:
- 111 - System PASS

KOER:
- 172 - HEGO sensor fault/lean
- 332 - Insufficient EGR flow detected
- 538 - Invalid cylinder balance test due to throttle movement during test
- 311 - Thermactor air system/fault during engine run self-test (main one I'm trying to figure out)
The check engine light will come on after a few minutes of driving and I can only pull the 311 code if I check while the light is on before turning off the engine. Every restart, it comes back.

The only codes that store in memory are the 172 and 332 but these do not seem to cause the check engine light coming on.

Any help or suggestions are greatly appreciated and I will answer any questions I can.

 

The computer wants you to stab the throttle when prompted, and it didn't see that, setting 538. See here: EEC IV Self Test hookup
Of the other codes, I'm not sure which one of those would turn on the check engine light during normal operation. 311 says air system is not working - the computer can monitor the O2 sensor during the self test to check operation of the air injection system even if the solenoids are connected electrically. I've never tried starting the diagnostic test with the engine already running - I didn't know that was possible.

 

I'd put money on the 172 & 332. Wiring or bad O2 sensor for the 172 and bad wiring, ruptured diaphragm or bad solenoid for the 332 illuminating the CEL.

Never, ever (across multiple computers, wiring & MAF conversions) have I been able to successfully pass the (538) "goose" test.

I've gotten the 311 off & on for years since deleting the AIR but leaving the solenoids connected, but it never lit the CEL.

42K, wow, you got a steal back then.