Bad idle

[bigred90gt]

My car has been acting really strange at idle, see thread "major problems". I changed out the harmonic balancer and it did nothing. About a week after I did that, the car bit the dust. The rpm's started bouncing from about 1000 to 2500 on my way from work, on the freeway at about 65mph. I got to my exit and the engine popped really loud and then died. I walked home and got my truck, and when I got back to it, it cranked fine. I took off and it did the same thing, only it popped about 4 times before dying. Now that is has been sitting, I can crank it and get down the street before it starts acting up. I have changed out the egr and cleaned the idle air bypass valve. One of the codes I pulled out of the car was for the barometric pressure solenoid. I know it is on the passenger side strut tower, but there is about 4 things in a bunch. How do I identify which one is the barometric pressure solenoid? Once I identify it, how do I test it?
Also, when I was changing the balancer, I had a blonde moment and forgot to take out the bolt. While trying to remove it, the crankshaft was rotating back and forth. Could this be part of the problem? If it was, wouldn't I have had the problem immediately? How can I check and see if this is part of the problem?

I really miss the power of my car and want to get up and running as soon as possible. All suggestions are appreciated. Thanks.
Caymon