They make one. 3.0 V6 @ 258 horsepower/428 lb-ft torque, 0-62 in 6.3 seconds. Top speed >140 mph. 35 mpg city/41 highway/38 combined.
But American car and light truck buyers have been so slow to move toward diesel, that Porsche isn't shipping theirs here yet. Maybe in the future, but not likely in the near future. Take the Cayenne Diesel for example. It was introduced in Europe in MY2009, but didn't arrive here until four years later.