[crunchymilk55]

If it was me, I'd choose EGT gauge, but you'll have to tap the source.

A/F gauges aren't very useful, in fact, I really only use mine to tell if I'm in open or closed loop mode. But, they will tell you if you're running Extremely lean, so I leave it there just in case.

Fuel pressure isn't really necessary IMO. Oil temp and oil pressure are two other good ones, but not necessary unless it's a monster setup.