The headers + exhaust will go a long way with improving engine performance. The best way to make the most of a Weber upgrade is headers, exhaust, EGR delete, intake manifold mods + port matching on the intake side, clean up the exhaust ports (minimise the amount of material removed from the port walls but feel free to smooth and polish the hell out of them) a wider duration street cam (high lift cam will kill performance in these engines) and redialling the distributor to compensate for the Webers' increased vacuum. I would wrap the headers too to aid exhaust gas scavenging (helps reduce under hood temperatures too) You can get away with not modifying the distributor but it will take trial and error to get the ignition tuning near perfect.

*open air filter elements are not a good idea. Hot air from the engine bay will rob your engine of torque and affect fuel economy so do your best to duct a fresh, cool air charge into the carb. If it's an enclosed air filter like the factory unit you can actually increase torque by making the intake tract longer...