From what i understand after asking around and doing some research. Around 1250 is the highest you want to go to be safe. I was told by a member here a while back once you start getting Close to 1300 and up the heat generated will start softening the metals and allow distortion which leads to a "found on road dead" ford. Exhaust manifolds warp/crack, up pipes start leaking, turbo wipes out and internals start to weaken due to internal temps. Just because egts are 1250 doesn't mean internal temps are not higher. Which leads to overheating, blown head gaskets and so on. I don't remember exact numbers but combustion temps are considerably higher so its one of those train wreck effects, one car derails and chances are more will follow but either way it ain't good.