You’ll have to define the build a little more to get better input but for a magnum with factory EFI and a 46re trans it’s hard to beat the jtec ecu with HP Tuners, prior to hp tuners support I ran an MS3 piggy backed on top of the jtec and that was a nightmare. I have experience with Holley dominator on a few different race cars and it’s awesome but I would not use it with the factory efi, it’s overkill. I absolutely love my AEM infinity ecu but support for that platform is gone since Holley bought AEM for the technology and adapted it to the dominator ecus (which may be why I like them).
@DNasty777 what don’t you like about the terminator x?