There are no turbos that I have seen for the stock Box engines. There are a few supercharger kits out there however. Mucho bucks!
Re: the 911 engine swap, a few have been done. Again, big big bucks.
Most folks here shy away from both avenues once the costs and other trade offs are tallied up.
The preferred routes seems to buy an S model and PERHAPS go the intake and exhaust route.
Not tons more HP but say in the 280 range at best.
I think above is an accurate summary.
