Have a chance to pick up an AMS F-1i intake manifold for a good deal but it's flanged for a Boomba throttle body, which I haven't read good things about.

Would it be possible to get it redrilled or reflanged for a stock(bored to 65mm) throttle body? Fill and redrill?

 

yes. You can weld the hold shut, and weld a plug in place, then just cnc a new 65mm hole and the mounting holes.

The better solution woudl be to build an adapter plate. I will take a picture of the one I made, it is not fancy. You just need to use thread sealer on the threads, and then you will need to just make sure everything is sealed up nice and tight.

pics:

 

Wonder what it would cost to have one made?