88 silverado tbi or ei problem?

I have a 1988 silverado 5.7 auto tbi 291111 miles.
While driving down interstate at 70+, smooth as silk, then the engine seemed to flood out and stall and then no start. Starter turns engine.Have spark.Have fuel from injectors.
At the suggestion of several different mechanics, I have replaced:
Timing set
rotor button, cap and plugs
distrubitor module
map sensor
O2 sensor
knock sensor
coil
ECM unit
checked diapham in tbi body
All the above made no difference at all.
Truck will start and run if I set the timing with the est wire disconnected. Reconnect est and the truck will start and run fair. When I turn off engine and try to restart the symptoms return. ie. backfire, detonation, rough running, will not idle, very rich exaust and the timing seems to be off..
I even drove it down the road with the timing set at 8 degrees and it ran fine but won't start when hot or very hard starting and flooding symptoms.This is with the est conduit disconnected. It won't usually even try to run with the wire connected. 'that is the tan/black stripe on the wiring harness.
I am at the end of my rope. Can any one offer a slolution?

*** est might should have been esc

Welcome to AF. How about the pick up in the dist? Checked the fuel pressure?

Welcome to AF. How about the pick up in the dist? Checked the fuel pressure?

Thanks for the welcome.

I have thought about the pickup coil, but the motor runs smooth and strong with the tan/black wire disconnected. I don't see how a physical problem could do this.

Also, I haven't checked the fuel P but how could it run fine part of the time under the same conditions with low fuel P?

If you unplug the electrical connection to the MAP sensor, what happens when you start it with the EST wire connected? You should check to see if you have good vacuum at the TBI port that is connected to the MAP sensor. Also make sure the vacuum hose for the MAP sensor is in good shape and can hold a vacuum.

How is the injector spray from the injectors? Are they leaking (i.e. do you see dripping fuel coming from the injectors).

//2000CAYukon

Thanks for the welcome.

I have thought about the pickup coil, but the motor runs smooth and strong with the tan/black wire disconnected. I don't see how a physical problem could do this.

Also, I haven't checked the fuel P but how could it run fine part of the time under the same conditions with low fuel P?
If the pick up fails when hot or at any time, no spark and/or injector pulse will occur, the fp test is to eliminate a possible source and focus on electrical. It is very hard from this desk to really give more precise info, a bad connection anywhere in the affected circuits is possible also. the truck is 18 years old so there are lots of possibilities. If you have spark and injector spray it should start, something is missing here.

Ok,
Thanks for the help.
Turns out it was a dual problem. Bad pickup coil and a bad module.