The most difficult aspect of those old emission control systems was the vacuum amplifier, which if I recall correctly, was used on that application. They just didn't have the durability needed for the long haul. But a correctly operating exhaust gas recirculation system will indeed reduce pinging, so you can advance the timing a little while the engine better tolerates today's crappy gasoline. Even today, some manufacturers still use an external EGR system for the fuel economy benefits of being able to run higher compression ratios and more advanced timing than without EGR. Others incorporate EGR through internal engine changes via variable valve timing. The best variable valve timing system yet developed comes from Fiat's Multi-Air system, which can open and close valves more than once in a single engine cycle - very close to an electronic digital valve system. But it is really electro-hydraulic. They won several engine of the year awards in 2012 when they introduced it on some of their 4 cylinder engines. I hope they incorporate that system in future 3.6 liter V-6s that Chrysler builds. Coupled with turbocharging, significant fuel economy benefits can be gained. Very cool.