I have an EGT sensor on my xcf 440 and I try to keep it at 1150 to 1200 WOT, 850 to 1000 at miderange. Remember Aluminum melts at 1300, so keep it below that. I have my sensor mounted after the "y" pipe 8 inches from the front of the pistons. I have Ceramic coating on my piston domes so 1200 is not a problem, on your 550 I would say 1150 at WOT would be good.