the reason for the increase from stock to carbon fiber intake is the amount of air that can flow.with the stock box it restricts air flow were the carbon fiber intake does not. you can only suck so much air through the stock setup.same with the exhaust if it is too restricted you will not get as much horsepower increase as you would with a less resrticted exaust.same concept you can only push so much air out.
as for synthetic vs dino: we use dino in all the boats we take care of due to the fact that you do not get all the benefits you do in cars (cold starts ,etc) . but we have a 32 ' skater with twin 1300 hp motors with a quad rotor supercharger setup that we use kendall 20w50 dino oil in. and when the motors are disassembled the bearings look like new.you could literally use them again. these motors get less miles but get more punishment with speeds of 170 mph. and unlike a car that shifts a boat does not.so they run @ higher rpms for extended periods of time on dino oil and still look like new inside. so it really depends on the application, and the conditions. shawn