Sudden Power Loss (opinions)

So i just checked temps across the manifolds 1 390ish, 3&5 450's, 7 420's, 2 400, 4&6 470's, 8 380ish. Obviously it's tough with cast iron manifolds as the temps will creep throughout the entire thing but within an inch of the head that's what i was getting. Sound normal-ish? At idle not moving it will stay between 180-190. On hot summer days it may creep up as well. I did go from a 195 tire to a 225 but the way it would smoke'em before i don't see that being the issue. Could be wrong.