I have the Air/Fuel ratio gauge with an O2 sensor, as well. I "know" this gauge since i had it in my totalled 1200. The EGT seems to peek at 1300-1400 deg on cool nights. At the same time the A/F gauge reads off the scale lean. During the day or on warmer nights, like to night, the EGT goes up to 1200deg or so and the a/f is in the Green or just slightly rich. If I floor it, as the rpm's climb, things start leaning out and the EGT temps climb.
All these temps are when I'm crusing on the freeway, at about 3000-4000 rpm.
I'm still fiddling around with the SU's. I havn't quite figured them out yet, but i guess I'm getting close.