Switch the cylinder 3 coil with another cylinder and see if the misfire goes with the coil. If not, try the same with the injector. If the misfire remains in cylinder 3 then it may be a more serious issue with that cylinder.
It sounds like tuners modify the stock tune file with the rtd device, can anyone confirm?
With other tuning devices like SCT and Ngauge, it is common practice for tuners to change the ecu strategy as they reuse the same tune files. I ask because I've personally experienced issues with my obd2...
@fmc_smt I found it on eBay and it looks like the red locking tabs are included. https://www.ebay.com/itm/255224744101?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ii0XmlP1RbK&sssrc=2349624&ssuid=Y9n8aFB3T2m&var=&widget_ver=artemis&media=COPY