1 inch of MP per minute reduction will usually take care of keeping the engine running right. If you can get a hold of the engine manual it will tell you how many degrees of temp reduction per minute are acceptable. Realisticly unless you have a graphic engine monitor (Insight or JPI) then it is pretty hard to tell how much temp change you are creating with your specific engine management. With the old guages you only get CHT from one Cylinder and egt from one exhaust port.