Do you still have the EGR?

Most of the time running seafoam will expose a vacuum leak if you run it through all the mechanical systems...yay smoke.

Or, you have a '97, I can't remember if I asked you this when you PM'd me but is the TB stock? Ported? Is it of a '97or '98 style or a '99+ by chance?

Because I know when I had a ported TB on my L36 car I couldn't find the vacuum leak for the life of me either, until we re-tuned it. Took care of that like a boss.