I don't know if it makes a difference with the LS1 or not, But I am a firm beliver in NGK plugs. I run them in everything. I know nothing is harder on a set of plugs than a jetski. (2 cycle and long periods of idling) I have had several Seadoo's and NGK's were by far the best. For some reason they dont foul out as easy. They work good in cars,boats, everything I have found. Just my $.02