Help gmc

First off hello to everyone I am new.Ok here is my problem I have a 89 gmc sierra 4.3 liter v6.I have been having some trouble with her she will just die when I am going down the highway etc.It started happening a month ago then progressively got worse.Sometime's I can accelerate through it then other time's she just die's but once she die's I can usually fire her up again and go for awhile longer.
list of item's changed so far
fuel pump
fuel filter
ignition module
rotor
igniton relay switch
I am not a mechanical wizard but i get by if this sound's like something any of you have experienced and fixed please let me know.
thank's

any help would be greatly appreciated.

Dies slowing down, at speed? Any other symptoms or components that die out with the engine?

I have had moment's when it dies at idle and when at 50mph or so.Once this happen's I can pull over let it rest then she will usually fire back up.I am going to replace ignition coil 2morrow,also I replaced fuel pump relay not ignition relay. I have had mechanic's look at it and it wont replicate what she does with me so I am at a loss.
thank's for your response

Somehow you need to find whether you have lost spark or fuel when this occurs, tough issue, as you would need 2 people plus it has to not restart of course.

That will be tricky my buddy was over yesterday and we did some looking and poking around.It ran perfect for about 4miles then we stopped the truck in my driveway and it wouldnt restart kept cranking and nothing.So atleast it did that and I had a witness he said my ignition coil was a little corroded and it's the original one.Could this cauz intermitant problem's like these.Could it possibly overheat during driving then cool and restart latter.

Anything is possible, seems you missed the chance to do what I suggested

It get's spark and fuel when this happen's.Someone suggested pick up coil could be bad.I will double check when this happen's tomorrow.
thank's

If you had these 2 components it would run ,one is missing, do you have fuel pressure at the rail, do you have strong spark at the plugs, do the injectors pulse, will it start with carb cleaner sprayed inot the intake. Check and or eliminate these issues and post back.

It does run but something happen's and the darn thing stop's.The injector's do pulse.what do you mean fuel pressure at the rail.Pretty soon there will be nothing else to repair because I just baught the ecm for the truck today just dont have time to install yet.

89 does not have a test port on the line, my mistake, you need an adapter at the fuel filter.

Ok today I changed the ignition coil it fired right up.Then I let it run for 20 mins then turned it off waited a few second's and she fired up which it hasnt done lately cross your fingers this could be it.If this is it I will feel like such a ron.
Than ks