Slippy

Hello, after fixing an oil leak coming from the rear main seal popping out I now have huge amounts of oil coming up through the vent pipe from the oil filler neck to the intake tube (2007 RX-8). I imagine this can only be caused by a lot of blow-by, however the engine runs perfectly all the way up and starts perfectly which seems to be uncharacteristic of a tired side seal. Is there anything else this could be? I don't believe the PCV system at the top of the oil filler neck is an issue as there is suction through the pipe. Next step is to get a compression test but thought it was worth checking here for any other ideas as the perfect running engine seems odd to me. Thanks