Check how much vacuum the VCV gets at idle and how much goes to the blue saucer. Check right at the VCV fittings. If you're losing 12" of vacuum at the VCV at idle, it needs a closer look. There are a couple of threads on reviving the VCV. In my case I happened upon a NOS unit on eBay and it improved the shifting situation more than the revived VCV did.

Sixto
87 300D