Injector(s) vs. Wiring vs. ECU vs. ??

[freeb]

Hey, Howzit? I think I'm about to remove the upper half of my intake in order to check my #3 and 4 injectors and wiring. Before I do that though I'd like to get some opinions and maybe some advice on what to look for, what else I might do while I'm at it or maybe a ''wait check this first.''

Here's what I'm looking at on my van which had been sitting for 10 years or so but had been running very strong for me for about a month. Good spark to cylinders and compression okay. (Double checked by mechanic). When I pull the #4 plug cap no change in running condition.
Sometimes #3 goes out also. Tapped on the bar that the injectors sit on and #3 kicked in.

The reason that I'm not sure I wanna pull the intake off to check the injectors and wiring is that when it started running on 3 cyl. (possibly 2) some weird things happened. First I had Christmas Lights.
Next my alternator belt snapped. Pretty sure after the dash lights came on. Though I realize they'd come on immediately once the belt snapped. Drove it a bit and it did get pretty hot enough to gurgle a few times but didn't let it up into the red.

It starts up easily. Runs on 3 cyl though I'm trying not to drive it unless I have to. It was really an all of the sudden type thing. Never had any hesitation. No fuel leaks (that I know of) Plenty of power.
Mechanic even strangely says that he didn't notice the injector problem until after he replaced the cat. He said it was running really well after replacing a belt and adjusting the throttle.
It was running on 2 cyl. when I pulled out of his shop. I'm pretty sure it was only on 2 or 3 when I brought it in. Don't know what to make of that.

Could this be an ECU problem? EFI relay fuse? Wiring circuit? Any way to check those with an ohm meter or volt meter? Most of the knowledge I have on motors has come from searching forums but I'm digging it. Actually glad to have something to work on now and I just moved into a place with a dry garage.

ECU looks okay on visual inspection but I think I remember an odd elec. type smell the morning it started misfiring. If I do need to remove the intake, what will I need and need to know? And as far as injectors? O-rings etc., I'd appreciate any help with where to get parts etc.