Holley Terminator EFI Questions

[Chetter's Z-28]

I have installed the Holley Terminator EFI system on my 82 Z-28 a month ago and engine is a 406 engine with a dual plane air gap intake, Dart Pro 1 heads, cam with .563"/.574" lift and 110 LSA @.050" which is a full roller setup and 10:5:1 compression. I have shorty headers and y-pipe and the O-2 sensor is located in the y-pipe getting its readings from the drivers side header. My question is what kind of exhaust temps are you seeing with EFI? I have been seeing temps in the 600-675 degree at the collectors which the headers are heat wrapped and I'm not used to seeing those types of temps when I was running the Holley carb. Plugs used to be slightly rich with the carb and now are a nice tan color. The car runs great but this thing with the temps has me worried. Talked to Holley and they had me turn off closed loop to see if it would stabilize but temps are still high. Is this normal? I am going to richen up the AFR to 13.0 for cruising to see if that helps and maybe even 12.5 since the manual says that larger camshafts may need more fuel. Anyone running this system and if so what do you see? I love the way the car runs but want to be sure I'm not going to hurt anything with these temps I'm seeing. The temps on the center tubes say about 1-2" back from the flange will be just above 500 degrees but at the flange, 250-300 degrees so I don't feel it is in detonation since I don't hear or see any signs of it on the plugs. Should I be concerned and if they are too high, what can I do to fix it? I never had these types of temps when running the 770 Avenger. Nothing else was changed other than switching to this system, no vacuum leaks, 17" of vacuum at idle which is stable and timing has not been changed, 17 degrees BTC initial and 36 total in by 3000 rpm. So there you have it, any ideas or suggestions? This EFI thing is all new to me and sorry if I ask a lot of what may be perceived as stupid questions. Thanks for any input.