Chrisman and I put a 20v 4A-GE together.
We went from N/A to Boost on it also, and went through a couple of head gaskets at low boost.
we ended up using a stock Toyota Head gasket, and pushed the 1.6L to 20 PSI, and never had a problem.
We also had trouble with after market rod bearings, and ended up changing back to toyota bearings.
I have done some research with head gaskets, and have not found a company who makes me feel comfortable.
For my application, I think Toyota Head gaskets, are what I want.