Seems to me that the weak point of the old Lean Burn system was having the electronics controlling everything on the air cleaner atop the engine. The heat and vibration combined for an unreliable system.
Well ...
That was the technology of the time - multiple components on a large circuit board with loads of soldered connections and virtually no heat sinking. There have been significant advances since then and I suspect everything is on a single chip the size of a fingernail. The whole throttle body would act as a heat sink - the airflow through it carrying the heat away from the ECU. This is probably more effective than mounting the ECU on the firewall or inner fender.
