Here's a Tommy Mars synth solo + voice bit that I always liked- at around 2:20. Gave me a chuckle the first time I heard it!
Weird, but cool.
I think he's using a Prophet-5 there, if I recall from the liner notes. Always dug the Coral Sitar solo in this as well. I really liked Vai in this period - raw, and rough around the edges. Kinda lost interest after everything he put out became so "polished" and sterile/clinical (just IMO). I have the same gripe about Satriani.
I came late to Zappa/Mothers, and this was my springboard. When I got Flexable in the late-80s and learned of the connection there I started working my way back through Zappa's catalog. I think my next one was "Them or Us", which had one of the live Whipping Post covers that you mention.