2017 Ford Fusion Sport
One step colder plugs won't hurt at all and are a precaution, especially since on the STOCK TUNE we are almost in need of one step colder IIRC. However, typically the advice we give here is "if your tuner says do this then do it." If it is a reputable tuner, and you trust what he is doing and he isn't running an extremely aggressive tune, then I'm sure he knows what he is doing. However, it won't make enough of a difference that it should even matter that you are using the one step colder plugs...if anything it is extra safety cushion.Usually I'd just listen to what my tuner says because they are the pros, but this confused me. I'm currently running a stage 1/2 tune (I guess)...mods are depo intercooler and aem dryflow filter. The tune I have gets up to 24psi. I'm currently running itv22 plugs and my tuner is saying switch to the stock ones. Won't I blow my motor?