I'm still not completely satisfied with the way it runs after the swap. I guess I was expecting a little better with a genuine GM crate engine. It runs OK for the most part but I can hear a slight spark knock under hard acceleration. I was supposed to be able to run 87 octane but it makes the pinging worse so I've been using premium. Watching the live data it has multiple cylinders misfiring at idle but not quite enough to set a code. Fuel trims are not as close to zero as I thought they would be or equal between banks. The computer tune didn't really help with any of this.
I've checked and double checked just about everything I can think of. Replaced and swapped tons of parts for testing including distributors, plugs, wires, caps, rotors, ICMs, coil, injectors and FPR, MAP, MAF, IAT, EGR, throttle body, knock sensor, PCM, crank and cam sensors, O2 sensors.
Fuel pressure seems fine. 65 at prime, holds around 60 key off. 55 idle. Between 55-65 while driving. Checked valve adjustment on a couple of the offending cylinders and it was fine. Did crank relearn, adjusted CMP to zero and even experimented with advancing it some but did not really make any difference. Timing seems a bit jumpy but not sure if it is the cause or result of the misfires. Pulled and replaced distributor but gear looked perfect like new still. I'm starting to wonder if the misfires are just inherent to the 383 not being balanced as smooth as a 350.
Maybe the PCM is just not well suited to this engine. Maybe the mail order tune I got is not accurate enough. Or maybe the engine needs more miles on it to break in more. Either way there's not much more I can do to it right now. I don't think it's running so bad that it will damage anything, so I'm just going to keep driving it and see what happens.
My next task is fixing the AC. Parts came in the other day and will be working on it this weekend.