how bad will a ristricted exhaust make engine temps go up?

 

ttt.... ok more info.. iv got a 350 with headers, y pipe, and no cat,its 3 inch coming out of the cat them it slams into a 2 inch stock cat back. im getting a new cat back, but i was wondering if this could be a reason y i run so hot. it gets so hot it messes with my breaks. i was gonna wrap the drivers side header when i put the cat back in, but if the 3 inch all the way back is gonna bring the temps down, then i dont need to spend 40 bucks on a wrap kit.