Hello Everyone,
I have spent thebetter part of the past 6 months trying to figure out the issue with my truck,I have spent hours searching on several forums but now find myself having toask to keep what little hair I have left..
1995 Chevy K1500, Extended Cab, 350 with TBI, 4L60E trans,234,000 miles, standard bed,

I have owned this truck since new, I have always changed theoil every 30,000 and run Mobil One oil, the only thing till now that has beenreplaced under the hood before this issue was:
1 Water Pump
1 Raditator
3 Sets of OEM original plugs
3 Sets of OEM wires
3 Dist caps and rotor
1 starter
3 Throttle Position Sensors
That's It!!

Transmission was replaced app. 70k ago with a new GM crateunit, system was not just flushed, I replaced all lines, coolers, everythingthere was.

Only other repair was to replace the speed sensor on thetransfer case app. 50k ago.

Only other service has been brakes, rotors, hardware, etcand no other chassis parts at all.

The only towing has been my 19 foot Skeeter Bass boat(reasonfor the tranny replacement) glad I don't fish any more..lol

When this problem raised it's ugly head, it did it in just 2or 3 miles, like a switch was flicked.

Now, items that I have replaced trying to clean this messup:

NEW GM Complete Dist Unit
New Plugs, wires.
New OEM bolt on GM Cat. converter
New OEM O2 Sensor
New right hand exhust manifold (saw a hair line crack whiledoing plugs)
New MAP Sensor
New Thermostat(just for the heck of it) have had no issuesat all with engine temps at all
New Coil
New AC Delco Vacuum Valve
New Vapor Canister Purge Solenoid

All of these items have less than 10 miles on them.
3 different GM dealerships, 4 other lifelong mechs and a few others along the way.

The truck starts like it did the first day, just tap theswitch and she roars to life in a instant, no missing on any cyls, no backfire,no sputtering, baby smooth idle always, oil pressure hangs around 50-60 psi atall times, lowest you might see is 45. Water temp just were it should be rathersolid on 210.
You can start it upand take off, also engine hot or cold has no bearing at all.
If you pull out on the hwy and apply the gas VERY lightlyand allow the truck to build up its speed very slow you can go down theinterstate with curise on at 80-90 and never know there is a problem.
Now, if you go WOTwhen you are running 55, in O/D, tach at app 1500 rpm, the tach jumps up to3400-3500 RPM in a instant, like a rocket, no missing, sputtering nothing atall, but the truck speedo stays on 55 and you go no faster, you can stay at WOTfor 5 10 seconds and the tach stays wound out, but no go. Same action if you gofrom a dead stop taking off and go WOT, tach goes to above and speed may be20-30MPH and no increase. Back of the pedal and let her get up to speed slowlyand it will twist the spedo till the limiter cuts her off. I had her on thelast mile or so the the above 10 and she hit 100 and running as smooth as ababys bottom.
The tranny neverslips, whines, nothing at all to notice. I also change my tranny fluid andfilter every 50,000 like clock work.

I swaped the TBI unit off of my 1995 Suburban, TBI has same numbers stamped on it , same running gear, 90k on it, no problems at all, put it on my truck, that says the TBI unit as a whole isnot involved, Put the TBI off my truck on the Suburban and it ran justlike it did with its TBI installed, so no problem there..Dang...glad I don'tdrink, but a trip to the American Boys Colledge may be in order soon.
Thanks in advance forany and all help.