they might refer to changing spark plugs and doing a major service as a tune up..
as Ash said you can only play with the CAS on the cars with standard ECUs..
years ago when my car was standard, i did have racepace Benno fiddle with the CAS on the dyno, with new plugs, the car went from 145rwks to 165..
so in my case it was well worth the dyno time, obviously reacted to the adjustment for one reason or another..