i am new to the sc game and i was wondering what was the difference between a 10% and a 5% overdrive pulleyfor the supercharger.which one is safer to use under normal driving condition.i just had the exhaust done(no cats with true dual and flos put on.i have heard horror stories of people blowing their head gaskets.any help would be apprec.also what is a good company that has a loy of aftermarket parts for the sc bird?