Sorry, kept you waiting for nothing. I thought the ICP was supposed to go full pressure when unplugged, unfortunately, it fails to minimum.
Back to basics, check fuel pressure and supply. Run off alternate fuel source to rule out garbage in your tank. Run return fuel into a bucket. Check for aeration. Lots of bubbles indicates combustion gases leaking into fuel galley.
BTW, what's the condition of the engine oil? Is it a quality oil, has it been fuel diluted, when was it last serviced?
Do you have boost pressure, is the waste gate damaged or stuck. Do you have a cracked cooler or blown boost hose? Boost relates to load, which correlates to ICP. Low boost, low ICP.
After your head was repaired, did you really beat the sh!t out of it? The heui engine is kinda like the old Detroit's. They wanna be loaded hard and driven hard. That's the only way to purge the high pressure oil galley of air. 25 miles of abusive driving. If you got a dyno , all the better, 60-70%load 2-3 minutes at a time will get it done quick .
Best I can do for you. Let's see what you find with what I've suggested