the sad technician

The random misfire code is the only other code. Just a knock low frequency code and random misfire code p0300

Well p0300 is the only code I'm currently worried about. The knock low frequency code is the only other code popping up but that just means the pcm isn't reading the right values for one of the knock sensors.

P0300 and yes they were oem/Delco parts and ok even if the plug gap is 35 thousandths why would that effect cylinder 7 and 8 more than the rest?

Yes a believe new cam and definitely lifters but the valve lash isn't adjustable? It's just a single bolt that I made sure I torqued to spec during the install. That was the only thing the machine shop didn't screw down.

im a tech working on a 1996 gmc with a 454 vortec engine. engine was freshly rebuilt and installed. ive been fighting with this vehicle for over two weeks now and im lost about what to do. we have installed all new map, maf, distributor, crank sensor, injectors, all gaskets on the intake twice, checked for vacuum leaks with starting fluid and by hand, fuel pressure is 50psi and goes up to 55psi when throttled, new plugs and wires verified cam and crank are aligned. both grounds are installed in front of engine and behind the passenger head. engine is changing fuel ratios and both banks stay pretty consistent. timing is set at 0 degrees at idle. but its still miss firing! ran a compression test and we got 100 psi at a altitude of 7,000 feet across multiple cylinders which is average for around here. I don't know what more tests I can run without tearing the engine down again looking for a problem that may or may not exist. both me and the customer are very unhappy. i hate throwing parts at a engine hoping thats the problem when everything is already new! again no codes besides a knock sensor low frequency which is there with or without them being unplugged. i got 5v going to the sensor with 3 kilo ohm of resistance between it and engine ground which is within tolerance considering 100 kilo ohms is said to be bad so idk why its throwing that code and just a random miss fire code. 7 and 8 cylinders were miss firing more than others but all cylinders were miss firing quite a lot. 7 and 8 have 2000 counts while all other have a few hundred counts. pulled the plugs and wires which are brand new and tried putting the old one back on and still no change. tried advancing and retarding the distributor timing and it didn't help. im running out of time and guesses. hell even gapped the plugs to 45 thousands which is spec.