screw mod is removing a screw in the front wheel arch that holds the arch liner in place
you basically remove the screw and put the plastic arch liner tab behind the metal tab from the wing and bend it back into place to hold it there.
this gives you more clearance when changing wheels or lowering as the screw is the first thing the tyre rubs on
if the rears are still rubbing and you don't want to change the tyres then just add a touch of negative camber and it'll give you clearance and stop the rubbing
Just seen the pics in your build thread and your car looks fantastic