Ahh, so they dropped a heat range just as we suspected to deal with the hestiation problem when hot!Sonic calls for 41-122. My 2014 Eco OM also calls for 41-122. However when I pulled the factory plugs they turned out to be 41-121 from Lordstown... shrug.
At any rate, here's how they cross reference to NGK...
41-121: NGK #IFR7X7G
41-122: NGK #IFR6Z7G