I would take it to a dealer have them do a readout and leak down test, run the serial number to find the service history. I believe many of the big block Optis of that era and had issues came. from putting the hammer down when the engine was cold. The Opti`s are such close tolerance motors many get blown from not properly warming them up. The piston expands faster then the cylinder wall which locks them up. My 2000 Opti has been great only problem I have had is 2 bad spark plugs. My routine, start the Opti make a few more casts, then good to go, or start and idle aways before coming up on plan.