Hey Jim. Thanks for the feedback!
The MP3 board would be the logical thing to do of course but would be out of character for me. I like doing things the hard (retro) way 
I already chose all my sound bites tonight. Ready to assign error codes! TBH I had thought about doing real voice but the only way that would be worth the effort for me to do is if I had the money to hire a hot Japanese girl to do all the messages and I just don't have the budget for that at the moment so maybe I'll make it a stretch goal.
The engine (an LS3) has had its MAP sensor replaced by me with a 3 BAR sensor so it has its normal 0-5V range mapped between 0 and 3 atmospheres. Once it exceeds 1 atmosphere it's in boost but nothing special happens on the sensor, it just reads a slightly higher voltage. My fuel tables do need to be special, yes, but I've already upgraded my car's computer to accommodate a boosted table so no issues there. I'm also running in open loop so I have maximum control.
No, I cannot retard the timing. That is something that only the car computer can (and will) do. However I do have the ability to shut down whatever is boosting the car when I detect KR so I can at least stop what's causing the knock.
The battery is necessary for 2 reasons. 1) the alternator is a parasitic loss that takes away from the power you are making and 2) it can't supply the 300 amps I need to run the blower
Most of the code consists of GUI formatting and IF statements to handle the many possible states the system can be in based on all the sensors etc but all in all it isn't gigantic or anything. Chipping away at it night after night makes it seem manageable.