Engine has rough idle and lack power?

Truck starts good idles fine, sputters and misses under power.

Engine Performance problem
1987 Chevy S-10 6 cyl Four Wheel Drive Manual

2.8 litre loading up on idle but has no more power after 1/4 - 1/2 throttle. The same power matted on the floor as 1/4 throttle. U can press the peddle to the floor and start backing off and from 1/2 to 1/4 throttle it makes power. It really acts like it is sort of floodin I guess, just notta lotta smoke from the tailpipe if any.

I have a 1986 Chevy S-10 Pickup truck with a 2 wheel drive V-6 Fuel injected 2.8 liter engine. It has an automatic transmission. Truck has 160,000 miles. Engine and
transmission are origional.
The truck has no pick up when in drive and performs at
about half of what you would expect power-wise on the road.
Top speed is about 55, and even then, only on a long straightaway. Start to go up hill at all, or to suddenly
accelerate from a full stop, and the engine coughs and rapid deceleration occurs.
This problem persists, and will not go away.
A professional mechanic shop is currently stumped, after having it for 10 days.
I am about to get it back because I want to get it
running. They have done no work on it.
When in Park, the engine will run very well, and when the gas pedal is held to the floor, it sounds and runs exactly like it should.
The transmission does not show any signs of trouble whatsover, and shifts in and out of all gears normally, and engages normally.
Only in Drive like I described, does the problem show itself. There is no sound from the engine indicating a bad cylander. All 6 spark plugs have been changed and correctly gapped, as well as new spark plug wires.
Distributor cap and rotor have been pulled, and inspected, are like new. While I had them off, I replaced the ignition module underneath the rotor. There are no cut or damaged wires visible under the hood, and all vacuum lines are attached and going where they should. Timing has been tested, is working fine, and is set at 15 degrees past normal settings. Lastly, old gas is not possible, it was nearly empty and then refueled with 15 gallons of non-ethanol just 4 weeks ago.
Any ideas? Thanks for reading!

I have a 1985 S-10 with the carburetated 2.8l v6 with 127,000 miles. The problem I have is that the engine is missing and knocking when under load. It idles fairly well but as soon as you start driving it starts missing and lacks power especially as you get to higher speeds. It is topping out at about 35 mph and starts to miss, knock, and buck. Timing is perfect at 8 degrees, new fuel filter, new fuel pump, newer plugs, wires, distributor cap, rotor, head gaskets, and intake gaskets. All spark plugs are getting spark and look fine when pulled. It also has a newer CAT and has been sea foamed. All the plugs are gapped correctly, no water in distributor, no cuts on any wires, firing order correct, no fuel leaks, fuel pump is pumping fine. I am out of ideas and with so many things being done recently im not sure what else is left.

This doesnt realy help me too much because I dont have fuel injectors, oxygen sensors, throttle position sensor, IAC valve, MAF. It has a new mechanical fuel pump so it has good pressure, the EGR valve is newer, all vacumme hoses are newer and all the ignition parts are newer. So pretty much everything on here my vehicle is not equipped with or has been very recently replaced.

84 chevy s10 2.8 eng has gargling sounds in the carb after I start it and give it gas as well as loses power?

Have changed spark plugs and wires, fuel filter, fuel line, cleaned carbuerator, changed air cleaner, oil change, doesn't know why it keeps bogging down and cutting off going down the road around 40 mph and up

Yeah we've replaced that first

I let a friend look at my engine and he said a vacuum line was disconnected. It fixed the choke problem as it was a cold start in the mornings and the choke would never idle down. But when I get on the hwy and try to accelerate it's like I am letting off the gas and it will not over 30-40 mph and it surges causing it to jerk back and forth real bad. Sometimes when I let it cool down and drive it again it does not do it, but it seems to have gotten worse. I think this guy sabotaged my vehicle. I have had it for about 9 months and never had any problems until he messed with it. Please help me. Can you send me a diagram of vacuum lines in a 83 S10 Blazer 4wd 2.8 LTR engine 5 speed manual transmission? Thanks

I don't know where any of that stuff your asking me about is, but I took some pictures fr you. I push on the gas and it just wont go. No power at all.