I had my pvc reroute fill with ice and snow one winter and it caused oil to push out the exhaust, but never smoked. I never even knew there was an issue until my low oil light came on lol
I'd be going back to that shop and demand them to tear it back down and find the issue. No way in hell I'd pay for a built motor with that low of compression and excessive blow-by. Do it before they say it's past warranty. Everyday you wait is a day closer to them being able to wash their hand...
Do you have access to a boroscope? If you do or can buy one then you can see in there where the leak is coming from. I got a good one off Amazon for cheap
Stock tr6060 is lower but ones like this claim to hold over 900rwtq https://www.tickperformance.com/tick-performance-level-5-super-magnum-tr-6060-900rwtq-and-up-for-98-02-camaro-firebird/
Is the fuel filter full? Sounds stupid but I've seen the primer bulb go hard and it was just air locked. I'd check for collapsed fuel lines also. Something from the fuel filter to the fuel tank isn't right.
Log with efi live desired frp and frp then go for a drive. Low fuel pressure from the cp3 will cause horrible mpgs and if you drive like normal it won't set any codes.