I will be looking into the alternator concern, because zapping electronic components is the last thing I want to do. Unfortunately, ATM we can't be without the Focus since my wife's daily driver is in the body shop for collision repair for the next week
so she is using the focus while I'm back to driving the F-150. I can see why an increase in power would occur when applying brakes due to power demand for the lights, but I don't think it would cause it to jump that high. Also, I'm sorry but I can't seem to wrap my mind on how an alternator that is over-volting due to a bad voltage regulator but still charging the battery would cause hard starts on warmed-up engine. Why would it need help from the gas peddle in order to start as well as drop in RPMs and begin to surge or chug after the brake pedal is released? This wouldn't seem to be caused by an alternator issue as suggested, because starting the car is battery based not alternator based. You can start and run a car without an alternator on a fully charged battery for about an hour before the battery is out of juice, that's if you don't use lights and power devices. I know the coolant sensor if bad can cause hard starts on a warm engine, but would it also make it run poorly like it is?