Just sent my Injectors to Rosewood Diesel for stage two's.
There is no need for a core charge if you can have your truck down while they rebuild your injectors. They will only replace the parts that are needed. (with your permission) Removing and re-installing the injectors is not that difficult for the average DIY kind of guy.You can get instructions from Beans Diesel Performance. (Excellent instructions)
Rosewood Diesel: there price is right, service is excellent and all are flow tested before they leave there shop. I have heard great response from there customers on other forums.