Oldsmobile/Buick Repair: overheating, head gasket leak, intake manifold gasket

Question
I have a 1996 Olds Achieva with the 3.1 with a overheating problem, I replaced the waterpump/thermostat/radiator within the last three months.The problem is its still overheating the guage will fluctuate from redline back to where it is usally I took it to autozone and the guy told me only thing in the codes was that the number 6 cyl was misfiring. now I am somewhat of a shadetree guy so I do most of my own work, I was told by a couple of mechanics that it could be either my intake or head gaskets that were leaking  

Answer
Hello John,
First, are you loosing coolant?
If you are loosing coolant, and the engine misses a little, and then overheats after the coolant becomes low, I would expect the intake manifold gasket.

If it overheats real quickly, especially under load, and/or possibly pukes the coolant out before the engine is hot, and then continues to get hotter, I would check for a head gasket leak.
Perform a Compression test. Or pressurize the combustion chambers with compressed air, while the valves are closed, and see if air gurgles out the radiator cap.(especially #6.)

Van