you can't make a totally safe tune just using a dyno, you need to spend hours on the street trying to replicate all types of driving conditions. Not to mention changes in altitude and weather. I remember when I was messing with KPRO on my RSX a tune that would look totally fine one day would start knocking if the weather changed, there has to be a large safety net for a daily driven car, unless you never leave a certain area or drive in varying weather.