You engine would knock. However I don't think it would knock under very light throttle, but when you get on it a little, ping ping ping. Nelson does offer dual tuning for 89-91 octane ratings. It just doesn't have as much oomph as a 93 tune since the timing isn't advanced as much. Heck, tell your wife that 93 octane is "better" for your engine. You could get her believing the higher the octane, the longer your engine will last!
Philip S.

 

Thanks for all the replies!! Looks like I am not the only one hiding from the finance department.
I at least have a couple of ideas to start with, including the tuning. Let the mods begin.

Thanks again all.