When I fitted a new engine to my 4.6 earlier this year I decided to get the Starter motor & alternator overhauled by a specialist auto electric company in the U.K. whilst I was over there. When the motor was started, the lights started "Pulsing", checked the alternator and the regulator was shot, this don't help the ECU's with them getting voltage surges so for speed I got a new 100A alternator from Paddocks for just over £100 shipped over-problem solved.