Let me understand this..... you've replaced:
Filters & Oil
and Inspected the screens in the tank and the UVCH connectors........
AND you have compression!
Well, I'm gonna have to THINK about THIS one....
You're obviously capable of doing anything to this truck, but (and here I don't mean to insult you) let's go over the Basics again. This is my entire "Check List" for a No-Start (sometimes you can't see the "Forest from the Trees
WTS Light? - do you get it when you first roll-on the key?
Tach Movement? - does the tach needle move up slightly when cranking?
Fuel - pump runs? Fuel refilling filter housing? Tank below 1/4?
Is it cranking fast enough? - it won't even TRY to start if cranking really slowly.
Is your truck "chipped"? If so, remove it as a Test.
Could the fuel gauge be giving a bad reading? (are you close to empty?)
Has the "Check Engine" been coming on at all? - codes would be the fastest way to direct you. Unfortunately, it takes a special scanner to retrieve them...
You could try disconnecting the plug on the ICP sensor to tell the IPR to go full open. Did you check the plug and sheet metal nut going to the IPR? Try "rapping" on the IPR with a screwdriver handle, sometimes if stuck, you can "free it up". Also, check the valve cover harnesses, and make sure they are plugged in.
Also, here's a cut & paste from somebody else (sorry to the author, I don't know who you are...)
-------These tests will diagnose probably 97% of the problems on a powerstroke----
7.3's only need fuel pressure, oil pressure, Power with electrical continuity and air to run.
The first and easiest way to diagnose (always the best place to start) is with a FORD scanner, Auto Enginuity, Snap-On brick scanner, etc... You need to have a scanner that actually WORKS on Ford Powerstroke Diesels in order to get these readings. Here are a few items you should get off the scanner.
Codes, are there any? Is there an SES (Service engine soon, check engine light) on when it's idling? If there are no codes then you should perform a Buzz test to double check good connection with the injectors. This could identify if you have an issue with your UVCH, Electrical wiring on the motor or IDM.
If you pass those tests then you need to check ICP and the IPR duty cycle. When cranking on the truck you should watch your ICP quickly jump from 0 psi to 15, 100, 250, 400+ psi and once it goes past 400 psi it should start. Meanwhile your IPR should be ramping up in a similarly quick fashion while cranking. You should see 9 - 14 volts with the key on depending upon the condition of the IPR. It should ramp up from 14 to 20, 25, 30, 32 etc... and level out around <35 psi in order to start. If it ramps up to 65, 75, 85 etc, there is another issue at hand. Watch your ICP/IPR while idling. ICP should stay around 500-700 psi and IPR should stay around 9-14v.
Finally if all that passes, we need to know what your fuel pressure is when you turn your key on, while you're cranking and once it is started. The truck may start and sputter if you're getting 20 psi or less... but most likely this isn't your problem. I have seen trucks with dead pumps get started and then the injectors siphoned enough fuel to stay running even though the gauge showed 0 psi of fuel pressure.