The original breather is one way flow - air is not entering the block only exiting.
The engine consumes the fuel tank vapors which results to better fuel economy.
Don't afraid to connect the manifold with the small line from the fuel tank- charcoal canister since the fuel tank is producing vapors slowly and even if you boost all day long you sure lift the throttle quite a lot times and believe me the vaccoum from the engine will suck the vapors instantly!
By the way my car (same as yours) is running with this setup for years except from the fact that I don't purge from the cylinder head just from the two sides of the block but thats about the same I think. Just make sure that if you purge from the cylinder head you need a deflector inside the rocker cover so oil is not coming into the hose.