Pontiac Repair: check engine light, pontiac bonneville, oxygen sensors

Question
1995 Pontiac Bonneville with 3800 (air conditioning). I have an intermittent check engine light. when I replaced the diode pack below the coils, the problem went away for a few hours and then came back (about 6 months ago). Every once in a while, the light goes out and I enjoy 100% power but eventually, it comes back. For long periods of low speed driving, the plugs foul and I lose a couple cyliders. This condition seems to correct itself.
Don't tell me about replacing the diode pack Ive done that 3 times. the coils are good. could it be oxygen sensors? a bad ground connection on the computer? Where is the computer located? I'm very frustrated about the lack of knowledge the garages around this area. Please help!
Thanks! bad connection on the diode pack itself?

Answer
Have you check for a code when the light comes on? A loose ground in the computre can cause a problem, the computer is located under the right hand side instrument panel,when the oxygen sensor goes bad it will set a code and the light will stay on.