where does the factory boost gauge attach to the manifold??? and is it OK to attach my autometer gauge there?????

The factory boost gauge attaches at the BOV. The factory actually version has a piece of hose coming from the BOV and then the boost gauge connection and then the rest of the factory hose.
And yes you can attach your autometer there. You will need a t-fitting that I do not think autometer will give you.

what if i'm running an aftermarket BOV, will there still be enough pressure to ensure the BOV works correctly?????

fyi: here's a link to the installation instructions for the stock gauge. It shows where to tap for the vacuum:

https://ssl.autocenter.net/webparts/acatalog/page1.html

I don't know the answer regarding your aftermarket BOV.....sorry.

Regards,
Kean

I do - yes, it will still work fine.

-Max