Cleaning the EGR tubes and throttle valve is a good maintenance, but as mentioned above, carbon buildup will not likely prevent the engine from starting. Think Air, Fuel and Fire.....every engine needs all 3 to run. To check Fire, toss a timing light on the plug wires see if the light blips....if yes, then Fire is probably good. Your engine's symptoms - and my money - is still on the ICM. They fail under hi temperature, so I've read of some people putting an ice cube on them and then attempt to start the engine.
Btw, in #10 above you mentioned that you replaced the ICM and the engine wants "to die out or stall when driving". As Al mentioned, if the Idle Speed Controller isn't working and is stuck in its retracted position, your engine will be starved and will die out. You can simply test this (and probably already have) by maintaining idle speed by keeping your foot on the accelerator. There is another test that you can perform on the ISC by getting it to extend and then unplugging it....keep in mind that you idle speed would likely stay at a way too high and would likely run away on you. Search this forum for "ISC Test" and you'll likely find the specifics.
Well, been working 7 days a week on the swing so I haven't had much time to work on the kids caddy. What I've done is pull the EGR valve and clean it up, works fine now and not throwing code for EGR. Checked wires with timing light and all seems good. Cleared all codes and not getting any current codes showing up. Here's something he didn't tell me, he's getting 10.8 mpg according to the computer readout, ok somethings up. He says he will here some popping or backfiring every so often while accelerating and car will have no power or will start bucking like it needs fuel or spark. Still the same problem with the car not wanting to start after it's been driven and up to operating temp, then he will stop somewhere to get something and come back out to start the car and it will just crank and not start, after 1/2 hour to an hour it will start again. I'm going to check the fuel pressure this weekend if I get a day off. I'm thinking fuel pump may be going. I'm stumped and I don't want to be just throwing parts in it that don't solve the problem.
Update, rented a fuel pressure tester today. Hooked it up and getting 22 psi at idle. Drove it and when accelerating the pressure drops even lower, looks like it's time for a new fuel pump, I don't think it's the regulator as I removed the vacuum hose and there were no signs of any fuel leaking. How much time am I looking at to replace the pump?