Strange Problem
 

Okay, I'm not really even sure how to describe this problem, so I'll list the symptoms:

1.) Harsh shudder in the engine, loss of voltage, loss of oil pressure (down to 30-35 psi), increase in boost reading (goes to about -5 to -2 psi).
2.) This condition lasts for approximately 2-5 seconds.
3.) Only happens while at a stop after I've been driving for over 20 mins.
4.) Seems to be most noticable when the A/C is active.
5.) Does not seem to occur when the car is in Neutral or Park

I'm really at a total loss. I've already taken it to a mechanic who "could not replicate the problem." Its getting to the point where I'm affraid it might stall out so I'm driving around with the A/C off (keep in mind I'm in Tampa.) Any suggestions?

when is the last time you changed the ignition wires?

<<increase in boost reading (goes to about -5 to -2 psi>>

This would be a DECREASE in boost which just fits in with your other symptoms associated with an engine farting for a few RPM's.

Tell us, what does your volt meter needle do when this occurs? [/u]

Re: Strange Problem
 

Voltage is usually at 14.3-14.6. When this occures it drops to as low as 12.9. But it returns to normal a few seconds later. Igntion wires? ...well, I had a complete tune up about 5 months ago.

I do know that it does occasioanlly miss and the boost guage is getting more and more out of wack. The highest boost I can get is about +3. Could it be a coil pack?

Misfire or skip come to mind.

Let's discuss the age and mileage of your ignition related tune up items.
Plugs
Wires

If that's good.. any visible cracks in any of your coils? Any flashing MIL light?

Plugs and wires were replaced in April of this year. I cannot observe any cracking of the coils themselves. No lights. The things that blows my mind is that one, it only happens while in Drive at a stop light and two, does not occur when the A/C is off. Or perhaps its just really noticable with the A/C on? I've been dreading the trip to my local Pontiac dealer, but maybe its time to think about doing it.

I had the stop light shudder and it was a mis fire. code p 0300
dont remember what time of the year it was so I cant tell you about hte AC thing.

edit: did anyone suggest a dirty MAF screen?

MAF was replaced at the dealer in May. Would you need a TECH II to pick up those codes?

Have you noticed if you mpg drops significantly more than it use to with AC on? Wonder if it is taking more poop than normal to turn the compressor vanes in the AC due to seizing compressor.