A power FC with Commander is great, it will give you instant readouts on AITs, Water temp, Vac/Boost in Bars, knock(completely inaccurate), speed in KM/H, and some others all with peak hold ability, but it will not give you A/R readouts.

As handy as the commander is, it's extremely cumbersome to read while driving. Gauges really are irreplaceable for on the fly readings. None of the gauges in my car work right now--stock or aftermarket-- so my commander has been invaluable until I get the electrical issues resolved, however it is a big PITA to read while driving. I mostly use it to periodically check my water temps and to check my peaks every now and then to make sure I'm not overboosting or check the high water temp.

 

I am not really ranking anything but if you have the proper modifications and a good tune I don't see the need for the A/F gauge kit. Water temp will increase much much slower then the a/f mixture! I agree the a/f will be different at hot and cold, tuning is done at normal operating temp. You should never push boost on a motor that is not at normal operating temp due to the risk of running lean. Outside temp can also play a role, colder air is more dense therefor making the a/f leaner then a warmer day. No tuner would want to push the limits of the a/f ratio and then have theyre customer doing the same stuff on a cold winter day and popping the motor, then they could get a bad name. I do agree it is nice to have, but it is not needed as long as your car is properly setup and tuned.

How would you know if your going to run lean, till your in boost and you should be keeping your eye's on the road. Boost comes on very fast in these cars! Water takes time to get hot where as a/f mixture changes very quickly.