Rt front headlite lo beam burned out, when switching to hi-beam, car quit, also lights fade and or radio cuts out when brakes are hit, intermittent - - voltage regulator? And where is that? Just had new EFI fuel injectors put in (all)
I'd have to make sure the battery has a full chage and the battery connections are all good. I'd also have to check the charging system. Check fusible links where applicable. The voltage regulator should be internal to the alternator.
If the vehicle cranks good but won't start, have a helper crank it while you visually check for spark at the plugs, if you have spark everywhere, use a gage and check fuel pressure. Check for mil codes. At the moment, I don't know what all your problems have in common?