Don't think there are many places doing that yet as it seems relatively new. Wouldn't mind getting mine done if it gets a bit more popular.
In the meantime, you could pull out your injectors and send them off to be cleaned. I had mine done whole the car was off the road over the winter and the MOT tester commented on how low the emissions were when I was putting it back on the road.
Not sure this would cause the car to run rich tho, might be worth doing a diagnostics check to see if any of your sensors are on the way out. Check the inlet hoses for splits, although this normally causes the car to run pretty rough