I have had a miss ever since I bought the car and was wondering if anyone has an idea what the problem is. I changed all plugs and wires. Switched injectors and ignition modules. Even installed a new plenum. When I took the old plenum I noticed there was about a cup of oil on the intake manifold. Where do you think that came from. Anyway, Could there be a air leak on the bottom of the intake manifold to cause this. Couldn't find any appearent vacuum leaks not to say there aren't any.

You didnt say if its a S.E./GT or GTP and what year???

Sorry, I have a 98GT

Sounds like it could be a problem with the intake gasket.IIRC they (GTs) do have a problem with that gasket.

~Larry~

How can one tell if they have a problem with that gasket and if they have a misfire, will a code come up for sure in the event of one?

That only comes after troubleshooting things like changing spark plug and wires, switching injectors, ignition modules and compression testing. After all that you have to check for vacuum leaks. Also there have been reports of the plenum leaking antifreeze into the intake manifold when you get some age on the vehicle.
By the way I have a trouble code of 302 that tells me there is a misfire on cylinder #2