I know you are getting frustrated, but its not the engine itself. Well, very unlikely.
With proper tune, fuel pressure, sensors and such, the engine would likely idle with just 4 cylinders having compression; poorly but still idle.
It does sound like an excessively rich mixture. As mentioned by others, it could be that the tune isn't for the bigger injectors. Also the IAT is critical, if it reads the default -30F, it will be pig rich. The wrong MAF, wrong connector, bad wiring, etc could cause the IAT is read so low. Such a low reading will not cause a code; it just thinks you are in Alaska.

A properly tuned engine will run just fine in open loop, e.g. with the the O2 sensors disconnected. After all you O2 sensor and wiring concerns, just disconnect them until this is figured out. BTW pig rich mixture can damage or at least "stun" the O2 injectors causing them to read wrong or nothing.

A properly tuned engine will also run in Speed-Density mode, meaning that the MAF is disconnected. However if your IAT is part of the MAF, you cannot simply disconnect it all. You could make a MAF extender cable which only connects the IAT and leaves the MAF disconnected. (Or maybe someone sells one.)

Everyone is giving you good advice and being very patient. We need more DATA. Step one should be to connect a scanner and see if the IAT values are correct.

 

OK, disconnect the two knock sensors.

 

Really appreciate the response and your advice as I try and figure this out. I hope you’re right about it being the tune, but at this point I’ve verified everything you all have suggested via my scan tool.

IAT reads 20 degrees C so that seems good. In my case, O2s being plugged in or not really doesn’t matter as far as I know - it won’t run long enough to go into closed loop. I’ve tried running it with them unplugged for the heck of it. No difference.

I have no way of diving into the tune any deeper than just seeing data from a scan tool. At this point, I have paid for two different tunes (via mail), and I don’t know what other choice I have than to bring the whole truck to someone who can verify the tune and plug in a laptop right there in person.

any thoughts or ideas, I’m all ears

 

Could it potentially be worth getting the injectors flow tested to verify they are not the issue?

i tested them via disconnecting the whole rail assembly and cycling the key - found no leaks. However, they could still be functioning improperly under running conditions, and be allowing fuel into the oil??

 

Something @68Formula said above, reminded me that after running the engine the best you can, remove at least a couple spark plugs, or even all to compare them.
If the mixture is super rich, they will be very black and/or "wet". Very lean and they will be very white. Take some out and post pictures here. Some people here (not me) are very good at reading plugs.
Glad you confirmed that the IAT is correct.

 

Unless the tuner locked the file, you can get an $80 obdxpro and use pcmhammer or lsdroid to read your tune. Also, I saw where you listed what fuel injectors you are "supposed" to have, but I never saw an actual part number to verify that they are what you think they are.

 

Understood. I did verify the injectors via my invoice from Glenn’s auto performance - Delphi 50lb truck height injectors. Don’t have the part number on hand.

 

Well I went ahead and did the leak down test and the results are not great (I think). What does it indicate if my compression test was good, but leak down test failed? I had 2 cylinders on bank 1 and 2 cylinders on bank 2 fail, and all leaks very clearly sounded like they were from either the intake or the exhaust (not the radiator cap, oil fill, or dipstick).

results:
1: 10%
3: 75%
5: 75%
7: 5%

2: 5%
4: 5%
6: 75%
8: 75%

let me know your thoughts

 

Did you pull the valve covers to absolutely verify that the valves were not being held open on the cylinders with 75% leakdown? Those numbers really don't seem plausible when taken together.

edit-- And the injectors should have the part number marked on the side. When in doubt, don't trust a shipping invoice. Anybody could have packed a wrong part.

 

Maybe bent valves?

 

Hard to imagine his 190-200psi compression readings involved bent valves.

 

I did not pull the valve covers. I used the exact same process and procedure to verify TDC on all cylinders. I believe my method was accurate enough as I determined leaks on half the cylinders, and no leaks on the other half by using an identical process.

I will check out the injectors later today and find a PN

 

Here's some photos of the plugs. Photo 1 is driver side/bank 1. Photo 2 is pass side/bank 2. Not really sure the condition of the plugs really matters much now in determining my issue, as the leakdown test failed. But either way, they are definitely fouled very bad for only having less than a few minutes worth of run time.

 

Should put in some fresh ones, so you can get a better understanding. The fact they are fouled could be contributing to the symptoms or making them worse.

 

These actually were fresh ones. After getting my PCM back with the fresh tune, I did maybe 3 attempts to test start it with no luck. I then drained the fuel, put in fresh 91 octane, new plugs, and these are the result after a few more additional test starts

 

Do you have forged pistons ?

 

No, they are flatops LQ9 type pistons. I got all my rebuild parts - gaskets, pistons, bearings, valve seals, etc. through WS6store.

 

The reasoning behind my question was that the LS is firing order swapped from the old smallblocks on the 7-4 and 2-3 cylinders, and I have seen that confuse someone about which stroke was supposed to be TDC on the firing stroke on any given cylinder. I have no idea what procedure you used, but when in doubt i ask the questions.

 

Gotcha, makes sense. I did not rely on using degrees past TDC on cylinder #1. Rather, I had someone turn the crank pulley while I felt for TDC on the compression stroke and also used the screwdriver method to verify TDC on all cylinders.

 

Well, ****. I was really hoping you bungled the leakdown test, because those numbers are a big problem since it sounds like you did it properly. The only way I see getting a good compression test and a bad leakdown test would involve the valves hanging open when turned slowly by hand, but not when the starter is spinning up a compression cycle. Time to look at valve guides and springs. I hope my speculation is wrong at this point.