Greenfish, I had 5 amps for my injectors also, and it ran fine until I got on it one time and the engine shut down and got me stuck a bout a mile from the house. Lucky I found the blown fuse and swapped it out and got home. Replaced it with a 20 amp and haven't had a problem since. Megasquirt says 5 amps but I think that is for 1 bank, and we run sequential, so we at least have to double it. Under load the injectors pull more amps as expected.
Good luck with your tuning.
Dan