It would be both generally. Say if you tuned one day and it was 90, then the next time you went out and it was 60, you'd want to richen both needles slightly to account for the temperature change. First work with the HSN and get the performance/smoke level good, then tweak the LSN to get the...
Depending on temp and air pressure, your tune can change (or really, I should say you need to change your tune). Generally it's not that significant from day to day as to require much fussing, but if you're breaking it out on a 60 degree day after running on an 90 degree day, it's going to need...