How do modern cars regulate temperature so well?

That EFI may bail you out right there. Running lean raises CHT and that increases engine heat. Electronically controlled EGR valving does the same thing, introduces non burning exhaust gas into the intake to keep CHT down and reduce NOx. Its all part of a package that keeps stuff at its optimum temp...and in a modern car that's like 230 to keep combustion at its highest level to reduce emissions. Older cars wont like that high of a temp with their iron heads and poor head designs. Its just evolution of the internal combustion engine, the less heat they release to the radiator, the more it can use to push the pistons down and the more mpg or power it can produce out of 1.6l.
Dont believe the hype on sequential EFI. No performance gains at upper RPM's as they cant fire fast enough sequentially to feed the engine on an open valve.