if the truck wasn't completely stock, I would think it could be something like timing.
that does make sense though.

I will track down those vacuum lines you're talking about. I know which ones you're talking about. I sprayed starter fluid and whatnot in that area, hoping to find something, but didn't. at least, the fluid didn't expose anything. i'll get more through with it tomorrow.

novice question, what side is considered bank 1?
and how are the cylinders numbered?
I've not been able to track down a FSM for this truck yet, and I've gotten mixed answers searching the internet.

Update regarding the codes
Change engine light is back on.
still showing bank 1 running lean.
misfire on 3 and 4
and that "cylinder A circuit malfunction" one.

There was another one in there, that didn't make any sense, and the woman I had helping me ran through it so fast that I didn't catch it, and of course, didn't write them down, like the first person did.
I'll be hitting up the part's store again tomorrow to get the codes read again to make sure.