Whats a super fast Analog I/O Processor?

[Gumby83]

May be it's worth to split system in 2 parts - injectors multiplexing (with optional timing adjusting) implement in hard logic (in CPLD or FPGA), and control for it in MCU. This split allow to build robust system. MCU program can hung or behave in incorrect way (because of software errors), but it will not affect injectors - they will be controlled by simple hardware.
MCU program for automotive grade application is not a simple task, even for quite experienced developer. It requires a special development process, and coding itself is less than 10% of it

When you say mutliplexing, what does that specifically mean? my understanding of Multiplexing is to take multiple input signals (i guess that would be 8 ground signals in my application) and condensing it into a single signal. Then i believe it needs to be Demultiplexed? Would a multiplexed signal be interpreted correctly for which injector that signal was for? my knowledge is very limited. 
 
I am looking into CPLD's, specifically reading this datasheet and while 90% of it is over my head, i what i feel i am correctly interpreting seems extremely promising. The temperature range this can operate in is ideal. I have much more research to do, specifically on how they are used and if they are suitable for real time injector duty cycle adjustments. 
 
I really like the idea of keeping the MCU out of the loop until called for, it seems like an added layer of protection specifically when just operating on the first set of injectors (which will be 99% of the time)

I will do my best to find the right people for the development, but i am just a single guy in a home garage. I guess we all have to start somewhere. I really appreciate what you said here, its given me alot of things to look into. Thank you!

[Gumby83]

Would that maybe be an application for an MCU with a small amount of configurable logic, like the RP2040 or some PIC MCUs?

It might be a silly question, but is configurable logic similar to the CPLD? is it considered hard logic? also..... what is hard logic? lol. i interpret hard logic as basically hardware control with no software... if that makes sense.

[Gumby83]

such projects should be done with special automotive grade MCU and firmware should be developed by very skilled software engineer developers and tested by skilled QA engineers team. If some newbie trying to do it on some arduino, in better case it will be finished with engine damage, in worst case it can lead to death of topic starter and passengers...

I agree, i don't intend on running this in a vehicle until it is automotive grade, i have injector test benches i can run simulations on. While i agree it could result in a damaged engine, death would be unlikely. If this was for a diesel engine which is fuel controlled, absolutely this would be terrifying and probably something i would not touch. Gasoline engines are air controlled, meaning if the engine gets way too much fuel for the throttle position (throttle body position, aka how much air comes in). it will just flood the engine and shut off. True this could lead to traffic accidents like being rear ended, but it wouldn't result in a uncontrolable vehicle. Alternatively, not enough fuel could lead to knock and the engine damage you mentioned. 
 
Either way, i am not strapping a arduino onto my engine to test it. I will be testing an arduino on the injector flow benches, as i have been recommeneded an arduino multiple times, but it won't be a part of the final iteration of this project.   
 
I am just doing as much research and learning as possible. Mainly to be able to talk with professionals in their field. I will be hiring someone to design the logic board layout and someone to program it accordingly.   
 
When it comes to testing, it will probably also be a a custom kit that can feed variable amounts of voltages while measuring the input vs output times for accuracy vs commanded while its subjected to EMF/Heat/Cold and vibrations. I dont want to put out something that will harm engines or potentially strand someone somewhere. 
 
So all i can do is the best i can do, and the more information i can get here in the early stages will only help me along the way. I Appreciate your concern, and i hope this alleivates it.