Not even close to the truth. EFI systems have tons of code in them and if something messes up the code nobody can fix it. I've bricked a few ECU's over time that even the factory couldn't fix. I've had weird system errors that the factory engineers couldn't explain. I've seen brand new ECU's go up in smoke when they are turned on. I've had injectors fail in weird ways that were super hard to diagnosis and couldn't be repaired without factory assistance. There are all sorts of weird Windows related things that happen with some of the EFI software that nobody understands. Stuff that will work sometimes but then won't work other times. Stuff that works with one release of Windows but not with a new release, or stuff that used to work but then your laptop gets upgraded overnight by Microsoft and then the EFI process doesn't work the next day.
When you are working with a carb everything that makes the carb work can be seen and touched. You can physically see all of the parts, passages, springs, check balls, etc. When you work EFI you can't see most of what is going on. Even if you have lab grade tools like a scope or logic analyzer you still can't see the code base. The guys at the factory probably have the ability to step thru the code line by line and see what is happening but nobody in the field has that ability. So there are times when the EFI system is doing stuff that nobody understands. And there is no way to understand it since we have no idea what the code is looking for.
I have a Holley system sitting here that nobody can figure out. It has been on multiple engines and back to the factory and it just doesn't work right. Nobody has any idea what is wrong. We've tested every thing that anyone can think of but the system just runs super weird. I had an Edelbrock Pro Flo system that also ran super weird on an engine. It took a bunch of time to debug but we finally did figure out that it had been programmed with the wrong firing order. I've seen systems where the Holley wiring harness was put together wrong and it took a long time for someone to figure out. Basically the owner of the car had to hire an engineer to debug the system because nobody else could figure it out. The average hot rodder isn't going to figure stuff like that out. I worked on an EFI install that had been to a bunch of different shops. It ran like crap at idle but ran great everywhere else. It took some time but eventually I figured that one out.
