I'm installing a rebuilt 3VZ-E, and the engine gasket kit has one that fits inside the rear main seal plate or flange. The FSM just says to use FIPG, and the part has little grooves machined into it for that purpose. Any opinions about whether I should use the pre-fab gasket, or the FIPG, or both?

 

Any or all of the above. Probably doesn't matter much.

I can guarantee you one thing though. Toyota used FIPG only.

I only use paper gaskets where I have to. FIPG only everywhere else. But that's just how I roll. Nothing against paper gaskets necessarily. They usually work quite well actually. And are certainly the easiest route. I almost never use them without FIPG though. And I have my own methodology when it comes to how I do that too. I give all my paper gaskets a rubberized coating. Apply a thin layer of FIPG to the enitire paper gasket, clear bolt holes and passageways, hang and let thoroughly dry prior to installation.