I dont have a vss in the car, it was swapped to a t-5 previous owner

anyhow no speedo and itll give a code 24 that will POP 4ish codes up

so heres my question,1. If i put a vss in and speedo works will i still get a code 24?
2. Not in topic but, how much power will going to 8 or 10 degrees timing give me if i run it on premium?

Thanks for any advice/answers

 

Any ideas? maybe this ismore of a tpi subject because of the code 24