Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Do you have access to a scan tool or a compression tester?
Sorry to be the one to bring bad news but you covered everything you can without a scan tool capable of reading live data, a compression tester, or a smoke machine. The only thing you haven't checked that you haven't already covered is looking at the injectors spray pattern and taking a sample of fuel from the rail and checking for contamination
Honestly I'm not sure how that works. I'm brand new here. But if you can contact customer service with a link to this conversation I think they'll be able to help you! Good luck!
Does your engine has AFM or DOD, becomes a 4cyl under light load cruising?
If so, I would say you have a cam roller lifter that has rotated and now has a permanent disabled cylinder 1.
AFM cylinders are 1,4,6,7.
If this is the case, it now becomes quite expensive to repair.
IF the camshaft has survived, you'll need to replace all the lifters, lifter guides and head gaskets etc.
Hope this helps.