Edelbrock manifolds are probably no better, or worse, than stock, just different. If they're the dual-plane design, they duplicate the operation of a stock manifold, and give good low-speed to midrange performance. Single-plane manifolds are racing-only equipment, with major torque losses at low speed to gain a little top-end horsepower. Definitely stay away from a single plane manifold unless you're willing to give up breakaway torque and acceleration, and only plan to run wide open at high RPM all the time.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!