more power (help)

I presume by "smog" Bewy means pollution that creates a visible haze rather than any specific chemical, and I'll take his word for it that he's seeing more of that. But even if the quantity has increased, its overall toxicity has dropped a lot.

Politicians pushing the wrong benefits, or latching onto a specific technology instead of a specific outcome, aren't doing anyone any favors. In the case of leaded gas, it (1) cuts out a rather nasty pollutant on its own, and (2) allows running catalytic converters, O2 sensors, and other emissions controls that create further pollution reduction, but won't do that on its own. So I could see a scenario where a switch to leaded gas on its own combined with an area ending up with more cars that do not have other emissions controls could end up with visible local smog levels rising even if the smog is less toxic.