I DONT think you can upgrade the no# on your plug. IF you have a 7, a BETTER plug is a BRISK=go to Amazon, type in performance plug. You will see 2 plugs 1 yellow, IF you have a NGKcr7hsa or another 7 rated plug, order it. Only 1 comes and its a match for ANY 7 plug. The no# is the heat rating, the more, the hotter, which can burn out ur engine over time if NOT match right. CALL BRISK in Texas and tell them your plug, if you dont have a 7 and they will give a match.