My '87 GMC Safari was running pretty rough last week all of a sudden. I would put the van in drive or reverse and the oil pressure would bounce around, idle was very rough. Acceleration was slow and lacking in power.
I opened up the hood and the interior to check everything out and found that two of my passenger side spark plug wires had come out of the tie-down above the manifold and were basically burned up from resting and rubbing against the exhaust manifold.
I replaced the wires and the plug while I was in there but noticed this opening on my passenger side exhaust manifold. I cant find my service manual but I'm thinking there used to be something attached there.