A 15 degree tip and 180 degree water should pop gum right off. I have a 10 degree tip that I bought from Mark that works great on gum. After a bit of practice, you'll find it easy to remove all the gum without damaging the concrete. Of course an oily like shadow usually remains behind, and there's no good way to remove it.
Cold water is not the proper tool for removing gum, no matter what. Gum has to be heated for effective removal.
In my opinon, a turbo nozzle should only be used by those who know how to use it. A heck of a lot of damage can be caused by untrained users. In fact, I don't even use mine anymore....haven't for the past 3 years. There is nothing I can't do with either a standard nozzle or my surface cleaner vs. a turbo nozzle.
Many years of experience along with thousands of hours of practice ensures that.