1992 Chevy Truck loss of power

Ok are you will to do some tests? I will need to know if you have a digital multi meter. I would like to test the distributor module and the timing spark control module. Let me know what you are up to doing and we will take it from there.

Ok first I would like to test he knock sensor it is on the engine block below the right side (passanger) exhaust manifold and what you need to do is unplug it and set your meter to ohms and check the resistance between the sensor terminal and the engine block it should read 3300-4500 ohms. If not then replace it.
Is the check engine light on? If so then we need to get a paper clip and jump the ALDL connector and turn the key on engine off and count the engine light as it blinks. It will blink 1 then pause and 2 =(12) then pause longer and do the next code in the same manner. Here is a diagram of the diagnostic port and what two terminals to jump with the paper clip which are term. A and B.

Let me know what you find and we will go from there.

Check the cap and rotor and ohm the wires no more then 1000 ohms an inch. I know you replaced them but check them just to be. I would also like you to check the TPS sensor.
With the throttle position sensor you will need to find the green wire and back probe it and hook up your multi meter and then turn the key on engine off and you should read .8 to 1 volt with the throttle closed now slowly raise the throttle and it should gradually and steadily increase to 4.5 to 5 volts. If it drops or glitches as you raise the throttle then it is no good. now also ohm the coolant temp sensor unplug it and ohm the term on the sensor to ground and give me the ohms and temp of the sensor at the time of the test. Let me know what this brings.
I also would like you test the ignition module in the distributor and the electronic spark contol module I will include pic of both ok.
The ignition module test the ground path circuit number 423 it should be less the 500 ohms. With the ohm meter hooked up still take a test light and touch circuit number 424 and the ohms should over range the 100-200 ohm scale to around 5000 if this tests good then all it ok if not bad module replace it. This test is done with the key on engine off. Here is a pic of the module and circuits.

Now the Electronic spark control unit. With your volt meter check term C and if when the truck is running the (may need to be in gear) there is 12 volts pressent the the ESC needs to be replaced. If there isn't 12 volts then take a small hammer to ratched and tap on the block near the Knock sensor and 12 volts should show. Check the ohms at term D to ensure a good ground and check Term B with the key on engine off to ensure battery voltage this way you know that there are no bad wires ok.

Let me know what you find. Thanks.

No not at this point as with what you are discribing I am thinking timing issue. So test the ESC first then test the module. The ESC with the knock sensor control the timing. If the ESC thinks it is pinging then it will retard the timing or advance it if it sees the signal incorrectly and make it ping and then it would be very hard to start as the timing is advanced beyond what the engine should be. Does this make sense? If not let me know I will try to explain it better.