Slant 6 no fire...

Make DAMN certain the ECU and while you are at it the regulator...........are GROUNDED.
Second that. Indeed, don't throw the original ECU out since it may be fine and just wasn't getting a good ground thru the rusty sheet-metal screw. That is a common problem, especially in humid regions. Also, next time you post, give precise descriptions without wishy-washy slang. You had people here uselessly spinning their wheels from terms like "no fire", "test light in the coil", ...