None, nearly none anyway. You will never look at them on the track.

Oil pressure is nice to glance at occasionally, buy when you see no oil pressure its already too late,

Oil temp - I guess this could be handy, gives you a chance to pit and cool down when temps start to get a little excessive.

AFR gauges are great, but again they are hard to watch like a hawk at 120,

You would be better off with an EGT and AFR if you are going down that route. Another great addition is a light to warn of det, either stand alone like the kmon knock unit or via your ecu assuming you can use a knock sensor with it.

Rob,