I have an 89 305 TPI. Recently the cars been bogging heavily under acceleration, so I changed the oil/filter, fuel filter, and plugs in the past few days trying to fix it. Today I opened the hood after a long drive (with the car off) and noticed a hissing coming from the passenger side of the engine compartment, somewhere around the exhaust manifold but it's hard to pinpoint. I could also smell raw gas when I stuck my face down there to listen. I went and unscrewed the gas cap, heard the normal hiss, and when I went back to the engine the hiss stopped and I couldn't smell gas anymore.

Does this sound like a broken fuel line? Possibly connected with the heavy bogging under acceleration?

 

i dont have any experience with your hissing,but passenger side under your plenum is the fuel pressure regulator...could be faulty..and could explain your bogging....cheap fix,but a bit time consuming....check around here for a how to....