[sgtmull]

Yes, there are more vacuum lines to be looked at. If you have a vacuum leak then under more acceleration your vacuum pressure would increase and open the dampers that are closed under idle, low pressure conditions. That sounds like what it might be to me. Since, you replaced the mainline, I would look at the vacuum lines behind the A/C control panel. Can you hear any leak from behind this panel? Another place to check would be Astrosafari.com. They have multiple threads on vacuum issues.