Shift light - Engine cuts out

Alright, recently I was having trouble with the 4-wheel drive. I traced down the culprit to the 4wd actuator under the battery. It is getting vaccuum at the wrong time. So I simply just unhooked the vac line from it until I get a chance to work on that problem.

It's not even been a week yet, or maybe it right at a week, and I'm already on to something new. Sort of.

It's an old problem I thought had went away, but it's reappearing now. It's something that happened when I first got the blazer, then went away, then came back, then went away. Apparently is a cycle of coming and going. It always seems to dissapear again before I trace down whats going on.

I have a 5-speed, so I have that stupid shift light. Lately when the shift light comes on, the engine momentarily cuts out completely. Just for a second, maybe not even a whole second. It cuts out hard though, like it loses electricity to the spark plugs or something, but I'm unsure. The guages never do anything funny when it happens, and since I know when the shift light comes on I can make the problem occur over and over again. That is until I turn it off, then back on again, and then it's usually ok for a little bit. There really are no preceding symptoms to it. Just one time I'll get in it and take off and it acts like a piece of junk.

What is happening when the shift light comes on? What all is going on that would make it cut out so hard like that? It makes the whole truck jerk hard. I can't figure that one out for anything.

List of what's recently been changed
Fuel Pump (Less than six months ago)
Distributor Cap/Rotor Button/Plug Wires/Plugs (with last fuel pump @ less than six months ago)
Radiator (Two Months ago or so)
Transfer Case Switch (Two weeks ago)
4wd actuator (Two weeks ago)

I don't believe any of that will help, since the problem occured both before and after the changes. Since day one when I got the blazer, and so far no one has been able to help. I hope that one of you will be able to.