Broken down college kid

I know this is way at the bottom of the thread, but hopefully others will see this other issue that I am having.

My alternator decided to die on me as well as my ECU. Finding out that my alternator was dying the ammeter gauge was reading in the negative side before my car decided to die on me. After having my alternator tested at two different places and failed each test I decided to get a new alternator. My ECU, after a long day of troubleshooting occurred, was the deciding factor as to why my car wouldn't start anymore. I have a slant six and was using the black ECU box for several years, we swapped it out with the orange mopar box that is typically recommend for the little bit higher RPM range engines.

My question is this. While the alternator, coil and ECU were replaced. My ammeter gauge reads at directly between the two lines at the top of the gauge when my car is just idling , yet when I push the accelerator the needle jumps to the positive side to the second to last tick mark on the gauge, yet when I come to a stop light it falls just below the top two tick marks into the negative side a little bit.

Before any of these things were changed out, for several years the ammeter was always reading right between the top two marks 100% of the time. What would be causing this sudden change now ? could it be switching to the orange ECU box ? or something else gone wrong. Thank you for any suggestions.