That sucks about your transmission. Years ago, I rebuilt the 700r4 transmission in my C4 Corvette. I took it to local old school transmission guy, I told him I wanted a basic rebuild with the upgraded clutches and I didn't want a shift kit. My Corvette was mostly stock but my friend mentions...
The rear vacuum port off the manifold has a T connects to the Fuel pressure regulator and MAP sensor. Since you found one problem with them, you want to get the all vacuum lines sorted out.
This is an old thread, but I might was well update it. I ended using a RPM turbo oil filter kit. It dropped my PSI about 5psi at the turbo (measured with a gauge) so it is under 30psi. It fixed my extended idling issue.
If you are restoring a SyTy, stock trucks are worth more. I modified mine and I don't regret it, but it would be worth more if I just left it and not spent money on performance parts. One of these years, I am going to bring it back to stock.
Try checking to make sure the ECM fuses aren't blown. I can't remember if our trucks have an INJ fuse, if we have one of those check that fuse as well.
I have a similar cam to that in my Syclone, except with 214/214 duration instead of 218/218. Mine idles well at 700rpm and I am happy with it but I may be tempted to do with 218/218 lobes like you have.
The Comp Cam 09-430-8 cam seems like NA cam.