When they changed the trigger. Macarri has lots of springs that will work, pretty much anything that will fit an R9 will work in the CFX. I've had good luck with the Tarantula spring, lots of folks like the E-3650, especially if you're looking for more of a "drop-in" replacement. Most will require a custom fitted guide and top hat for best performance, but there are ways around that. Just do a search on shrink wrapped spring guide. Link to Macarri: http://www.airguns.citymax.com/page/page/251327.htm
Hope that helps, and good luck.
P.S. DON'T try to do without a spring compressor! The CFX has more than enough spring preload to ruin your day.