hello again a buddy of mine has a Goodwrench Crate motor 14010207 4bolt with an edelbrock performer intake and a 600 cfm holley with great throttle response wondering if his is something special in any way of if the intake and carb made all the difference. I have a 350 4bolt 14010207 out of a truck, motors in excellent shape with stock intake and holley 2 barrel 300 cfm not as snappy. but anyways the valve covers on his motor say GM Goodwrench 350 MD curious what the MD means? thanks