I use the Autometer brand EGT that you can get from Summit, Jegs or wherever. As far as tuning you would want to shoot for about 900* when around town, 1200* to 1300* on the highway cruising. Max power is developed at about 1500* to 1550*. The longer your in boost and on the gas the higher the temps will get. I shoot for about 1550* at the end of 4th gear on a full run. I've been told that hitting 1600* is ok but, don't go over that. These temps are with the probe installed before the turbo in the collector. Something to consider is that timing will effect your temps as well A/F ratio. Retarded timing will be increased temps and advance timing will lower temps. Since every car is different then you just need to get as close to stock as possible and then start playing with it from there. Document as much as possible if you have the ability to make several changes like with a aftermarket F.I.
Ofcourse a session on a dyno with a wideband O2 and the EGT would be a good way to know for sure where your at with your A/F ratios and power levels. Small changes in boost levels can bring big changes in temps when using a large tubo or one that is out of it's effency range. It's always tempting to increase the boost some but, that can lead to bad things if your not careful.