Marty - did you ever get your problem resolved? I have exact same problem with my 66 GP Tripower. See thread
http://forums.maxperformanceinc.com/...d.php?t=639843 for all the suggestions. It is running better now, but still stalling at lights. I did have a hairline crack in the manifold under the center carb that widened after warm. Kicked fuel mix up, but it smells too rich. Did the spacers help, that might be my issue also. Mine started the same way - ran fine, then one day started stalling and got worse and worse.