Stock Intake manifolds

[SSC's76]

It's a double edge sword kind of deal. The inert gas from the EGR system does increase intake charge temp but decreases combustion chamber temps. This cooling effect of combustion gases allows more spark advance under cruise and increases combustion efficiency. That’s why the auto manufactures went with electronic spark control and an array of sensors to monitor and adjust for proper operation. In pollution controlled vehicle with all the sensors intact it does work especially with a computer controlled carb or fuel injection system. In a dumb system it does very little to effect fuel economy but can hurt drivability since the EGR will only be metered by vacuum and the levels of advance that would yield better cruise economy will bring detonation without constant adjustment. So for performance or non emmision use toss it. If your running a CCC or FI setup keep it.

BTT.

Lots of GM cars came with an aluminum intake manifold. For weight savings it might help but for a good seal your not going to beat a cast unit and there is no flow difference between the peices unless you get ahold of a ZZ3/ZZ4 intake which are both nearly identical to a performer.