106FF and an orange 6.5nch cutting pad is no where near reaching the cutting limits of a PC. That explains why you are having issues removing swirls. If going to IP doesn't make much difference then SIP wont cut it either you'll have to go with stronger pads and stronger compound.
Buy some
Meguiars M105 and some 4inch cutting pads. The 4inch pads give far more cut and M105 has more than double the cut of SIP yet finishes down really well. The 4inch pads work great with M105 considering its a rotary only compound.