adding more fuel will lower the temp. so yes, going higher in jet size from 155 to 160 will cool the engine. and u can also try, moving the needle lower, to make richer in mid range as well as will make richer in the top end. Most needle are 3 notches. Clip to the lowest notch so the needle come out the furthest. I would do that before a jet change. That simple 2 millimeters will make a difference.