Will a Mummert manifold and the best car headers add any performance to a stock 312? Motor has ecz-g heads, 1.54  rockers, the better exhaust manifolds, Holley 4150. Not sure on bore size, or cam specs but assume cam is stock.  If I can buy 25 HP and some torque it would be worth it, for 10 HP probably not.  Any thoughts appreciated, I've been thru the Eaton test pages (amazing) but none really test an otherwise stock engine so I'd be blind guessing any value.  Thanks

Ted, Redding, CA