Well an S-afc does not "cause detonation" its the bumblehead behind the programming of it that does generally. BUT, I have heard stories about the timing issue before but someone solved it....

That said, Instead of dicking around with an SAFC, I'd stay stock w/an FPR or spend the money to get the http://www.mrcontrols.com/ standalone for the car. Plugs into the factory harness and retains ALL factory options, no other standalone can say that. Plus look at the list of features, its more than enough.