I did check ou the vacuum lines. I'm not sure if the line was cracked before I started or after - all i know is i ended up snapping two of the vacuum lines trying to inspect them - they were amazingly brittle. I guess after 15 years, things are bound to fall apart.

After I replaced the vacuum lines, it did seem to get better, but has since returned.

What's a good way to check the EGR circuit? I pushed in the EGR valve, and it didn't take too much pressure to move, so i think that it's working okay. Could there be more to it that's causing the problem?

Thanks!