All sorts of "fixes" have been tried. It seems the best route is to add either an underbody condenser or a condenser in the left rear fenderwell. Of course, change out your old hoses and get barrier hoses. That will keep your R12 or R134 from leaking out.
Griffiths sells hoses and a fenderwell condenser kit:
Griffiths
Scott's Independent Porsche Repair does underbody condensers:
Scott's
Also, you might consider adding a Procooler, though there are mixed opinions about how much it helps. Do a search here on the board and draw your own conclusions.
Good luck.