in theory they should give you more power. the SS pistons have a special cut to them on the exhaust side that is tapered off to be 2mm lower the the rest of the piston crown. this gives the cheated effect of raising the exhaust port 2mm.
on a side note, how come no one has done this for the transfers as well. it would give less compression, but that can be fixed in the domes. anyone know, or am i crazy?