I agree that the only way to solve these problems is with data. Most people don't have a amp clamp but they are fairly inexpensive these days. I've seen them as cheap as $20 but somewhere in the $50 range is probably more common. It is just like anything else, if you don't have the right tool then you can't do the job. I picked up an amp clamp meter last year when I was having some starting problems and I used it to check the current flow all around the car. On my car a 60 amp Denso is more than adequate even with fuel injection and an electric fuel pump and all the other stuff.