Scott,
First off a disclaimer that I have little knowledge of 2nd Gens.........
I had a similar experience with drop off in fuel pressure and in my case a new pump solved it.
> If the cap isn't vented how does the fuel tank vent?
Another connection I spotted that concerned me on my car was the connecting hose between the tank hard line and the chassis hard line in this pic:
I replaced it years ago, but it felt soft enough that I was concerned about it collapsing under heavy demand so I replaced it.
First guess is a venting issue as the tank has to vent for the oneway system to work. The car sat for a while right? Bug debris effecting venting?