Actually, you will get the highest EGT at right around 14.7 to 1 since there is no 'extra' fuel or air to cool the mixture. Obviously fuel has a greater effect since it requires 'latent heat' to change state from liquid to vapor. Air provides SOME cooling, but not nearly as much as fuel.

Last weekend we were mapping a 2.2L turbo Impreza with an Electromotive setup in it. We were seeing about 1600 degrees (F obviously) of EGT and the AFR was around 14.5 or so (about. 0.98 lambda) and I added fuel until lambda was about 0.84 and EGT was around 1500 max.

When I was playing with the dyno just about every day, we found that max power was almost always around 12.7:1 AFR and that anything beyond that (richer) was just additional cooling.