Need Help: 350 TBI Running Rich/Bogging

[5Tractorguy]

I've been chasing this problem ever since the truck went on the road 6yrs ago. Hoping someone on here can help.

Truck is an '88 V30 1-ton 4wd dump truck.
(Yes, I know it's the wrong year for this forum, but it's more relative to this section than mid 90's GM's).

It has always had a power problem pulling, driving, consuming way too much gas. Some times worse than others. The 350 was completely rebuilt when the truck was restored. And the air injection system was removed but the engine wiring harness wasn't changed (could be a problem)?

Anyways, I've been through 3 different computers, it's currently running best on one from an '87.
Injectors are re-manned
Fuel pressure regulator is rebuilt
Fuel pressure is good
Ignition coil is new
New cap and rotor
New Spark plugs
Timing is set to about 2-3deg (set with advance wire unplugged).
I think at this point every sensor has been replaced (maybe one went bad again)
Vacuum lines are where they should be
New EGR valve
New O2 sensor

I just did the TPS again on Friday (you could wiggle the plug and it would hunt so I figured the sensor) and now it's running even more bogged. Using gas to the point that I watch that gauge more than the speedo.

When I did the O2 sensor about 2 months ago it woke right up and ran great. Bunch of power and then it slowly started the decline again. I'm wondering if since the air injection system was removed it's not reading something right and in turn calling for too much fuel resulting in fowling the O2 sensor??

I've been getting real close to converting this thing to a carburetor and doing away with the TBI, just want my power back.


Any help/direction would be greatly appreciated folks!