bobpur

Despite throwing parts at it in hopes of fixing the problem; it still persists.
After a new engine and most new electrical components it, infrequently, starts hard. Eventually it will go. Sometimes as if nothing is wrong and other times it'll stumble along as if it is relearning which spark or squirt of fuel goes where. If it starts as if nothing is wrong life is good. If it starts and stumbles along it eventually straightens out and life is good.
Right after the new engine and new components it run almost a year without a problem. Then it happened and has been becoming more frequent.
Last evening, after sitting for 4 days it refused to start. It would come up to where it was just ready to catch and it would quit when you let off the key.
I tried starting ether thinking I might have a fuel problem. Ether made no difference. The engine wouldn't fire off of it.
Replaced parts include: 2 batteries, in line gas filter, fuel pump and screen, fuel pump relay, throttle body (Came with new engine), other items that came with new engine (new engine is out of a '99 Tahoe), new cap, new rotary button, new wires and new plugs.
This problem started with the old engine so I'm thinking (now) that it's the computer which is about the only item I haven't replaced.
I'm at my wits end. This problem throws no codes and defies mechanics in the area.
Shipping it off to a dealer who is backed up for almost two weeks is getting more appealing also.
Anybody got any ideas? I'm running out.
Thanks.