Just how big an alternator do you need to run an aftermarket EFI? 90 amps seems serious overkill.
With EFI, you have a min voltage at which it shuts off. If you go below that while at idle, the car will quit.
You have to add up all the items in your car and look at the amperage. This is what the battery will see at an Idle, you need that amount or darn close to it. If not, your battery goes dead pretty quick. I started with the Mopar OEM alternators, and those were horrible. Been running chevy 100 amp 1-wire alternators for ever. Recently though, I had to upgrade my fans and then my electric water pump. The new fans really put a load on things. I ended up trying a number of alternators. Ended up with a 140 CVF unit...Man, my idle voltage is dead steady with everything on now. For the money, nothing I have tried beats it. And had some pretty pricy ones, and found out that they stretched their specs, cause when I called them on it, they told me that most of the numbers were for above 3500rpm.....
https://www.cvfracing.com/gm-1-wire-alternator-140-amp-chrome-plated/
