one other thing I'd add -- how old is your tip?  An old tip never seems to cut as good as a brand new one.  Just a little bit of slag or defect or whatever in one or more of the pre-heat holes or even in the oxygen hole will create a swirl that will prevent a "clean" burn/cut.

Try a brand new tip and surprise yourself into thinking you have enough experience to fool others into thinking you know what you're doing.