Yeah I just went to go replace that o ring but I can't get it to twist closed right. Tried spray carb cleaner around it nothing happened

 

Did you try wiggling the top of the injector assembly while its running to see if it makes a different noise? the top of the assembly is right below your arrow in that picture, the thing that the fuel lines connect to.

Edit: I drew a circle around the part im talking about just so you know. But just from looking at the picture, the top of your assembly looks to be sitting a little low in the intake which could be creating a vacuum leak which would make that noise (exact same thing that happened to mine) its hard to tell from the picture tho. So while its running wiggle that part or put your hand over it and see if you can feel air going in there.

 

If you can find an old stethoscope or buy a cheep one (i have several being an EMT) and pull the head off and replace it with a tight fitting metal rod. this is a great tool i have used to isolate weird noises in the past. if you put the stethoscope on and touch the rod to different engine components you can actually hear bearings and stuff rolling around in side things like pulleys (don't put the stethoscope on the actual pulley put it on the shaft it is held on by haha) you will know when you find the problem part because you will only hear that noise through the stethoscope when it is touching the source or a bolt connected to directly to the source. I know this method is a little hillbilly and its not rocket science but it has help me isolate problems in the past. good luck bro.

my bad i just realized I hadn't read the whole thread, sorry guys looks like you are well on your way. I thought i would leave my post up just incase someone else had weird engine noises too

 

Ok finally got some time to work on this beast again and picked up a new o ring for the brake boost line AND ended up noticing that a vacuum line was corroded and the ended when I wiggled it.
Replaced them and still getting that noise.... But i have another hose back by the distributor that looks sketchy so i will replace that tomorrow too.
Tried putting my hand over the part cherryblazer circled in the pic but didnt notice any changes. BUT I sprayed carb cleaner around the area and a few seconds later the engine lowered its tone and the smell from the back of the jimmy was sulfurish smelling.

Side question: I have a fuel pressure gauge tester from autozone to try but I have no idea where to hook it up? Hopefully that's not to ignornant a question I tried one port I found but the thread size was different then the tester

 

Hmm do you think you can get a good side picture of that connector i circled so i can see if it looks lower in the intake than its supposed to be? The fact that the engine changed idle when you sprayed carb cleaner in the makes me think it has a leak there. That part doesn't move easy so you have to push and pull pretty good to get it to move. Like i said mine made a very similar sound when mine wasn't sealed correctly. Does it even sound like its coming from that area?

 

On the back of your engine kinda on the leftside theres two shrader valves where the guage hooks up too.

 

here is a pic of the intake

also here is a question is this electrical plug supposed to have a gasket on it??

 

I STILL HAVE NOT FIXED THIS AND THE JIMMY HAS SAT EVER SINCE! Does anyone know where I can find a diagram of the vacuum lines?

 

Like Maverick, I have not read all the posts on this thread. I did want to throw in for your consideration this incident which happened to a friend of mine with a 1996 Chevy SUV with the V8 Vortec engine which is a first cousin to our 4.3 L Vortec engines. He had a mysterious whistling noise that he could not locate. Finally he found it. It was a PCV valve that had a crack at the seam. This air leak caused a whistle, but only at certain speeds. He replaced the PCV and that solved the ongoing mystery noise. Please let us know what you find is the source. Good luck.

 

Yes my next guess was going to me the pcv valve as well