[Gregski]

without preaching about carbs, let me point out the difference between the 4150 carbs and the 4160 as it may effect our tunability capabilities, and even require us to convert our 4160 into the 4150 (it's duable folks)

in technical terms, what's the difference?

well simply put the 4150 has something called a metering block in the front (between the front float bowl and the main body) and another one in the back (between the rear float bowl and the main carb body) (a metering block is what holds the main jets, etc) a 4160 only has one metering block in the front, and something called a metering plate in the back (you can't screw in different jets into a plate, hence the limitation you have to swap out the entire plate but its not the same granularity as you would have with changing jets)

first pic is of the metering block (thickness of a wallet)

second pic is of a metering plate (thickness roughly that of a credit card)