Oh! Definately haltech datalog. And can tune sooo proper with it. So long as sensors are calibrated in range. Lol. I've made that mistake a few times with my o2 sensor. I use a ton of haltech equipment, since it's so user friendly, and made by people who actually do seat time.

Most valuable data i look at, is o2, vac/boost, rpm, ignition angle, and injector duty cycle. That stuff will make or break an engine quickly! I learned on rotary, that you can definately foul out spark plugs way too early by letting auto-tune take over. The oil in the exhaust will mess up the o2 sensor, and make you run waaay too rich!