86 5.0 swap Starts but wont stay running

[Redbird]

Helping a friend finish up swapping a 5.0 from an 86 into an 88 Vert, been working on it on and off for a few years and he's finally going to get it done this spring, rather, I'm going to get it done and he's gonna stand around and hold tools. It's been running before but needed a whole lot of finishing.
After sitting for quite some time, the engine will turn over, start and run for a few seconds then die. Fuel pressure is good, timing looks to be good, injectors are firing, MAF should be good, but who knows. Not overly familiar with Fords EFI system but i"m intimately familiar with GM's. Any pointers on where to start diagnosing this thing?

 

[dsblk93gt]

How long has it been sitting for? It could be the injectors. Have you checked the plugs?

 

[Redbird]

Been sitting for several years, in that time it has been fired and run a few times. Plugs looked good last time we tried running it. Injectors are getting pulse but could very well be clogged up, wouldn't be a big surprise. What are the symptoms of a bad MAF sensor in these cars?

 

[1990_LX]

Staling, rough idle, running rich. It can do a lot because the computer doesn't know how much fuel to give it. If you think that's the problem you can unplug it and see if it will start but if it has been siting for a while it could be clogged injectors or even bad gas/watery gas.

 

[Redbird]

Pretty much what I was thinking, thanks for letting me pick your brains. We'll see what happens next week when I work on it.