The intake is the factory GM dual plane that comes with the "602" crate. Stock, as delivered, no mods to the plenum divider as it's against the rules, and now it's "sealed" so not removal is allowed. I have used a 1/2 dozen spacer styles to "tune" the intake/HP/TQ curves/settings. The carb starts off with a 650HP part # 80541-2 right from Holley. Then I do all my work for my "602 Crate" program, and there lies the magic as you see by the AFR's. It idles at 13.4-13.6 AFR's so it's good & clean, the trick is in the transfer/bleed/PV circuits to set the RPM activation of the mains, this is an awesome race carb, but not quite the best choice for a "street" type deal, that's a different setup that I custom build. FWIW same exact carb is spec'd for the 358 DIRT Modified, but not the same setup at all as they are in the 580-600HP range with 10X Octane with whatever % oxygenated fuel. Open plenum intake, so spacers vary in style. Does this help you out Ed, if not, sorry for being vague, but I work for many "Race Teams" and the NDA must be held in high regard.