How did you come out on this one, people would like to know, we hate to give help and not know if it was helpfull or not. Who knows, maybe what you found will help someone else out in the future..

I would be looking at the possability of the camshaft being out of round causing the dist shaft to run in an ecentric pattern instaed of a circular pattern. I hope my spelling isn't too far off on these words, but you should get what I mean by them.

Sounds to me like the PCM might be corrupting the EGR flow and causing backfourced resonance in the air box.... I would get a PCM from a reputable salvage yard and give that a try.

I think the PCM is gonna be your problem