I may go to the wreckers and pick up an MR20 head to dedicate to a port and polish. The ports are pretty well optimized from factory. As was mentioned, the best thing to do is to get a dedicated head for this kind of fooling around, and take it to a place that does this stuff. I'm wondering if bigger valves may be better, QR25 intake valves maybe? Porsche 928 stroker guys use Porsche 968 intake valves (968 used a 3L I4, so 6L is what stock 968 valves could provide for in V8 form).