NO. You CAN NOT run on just an add-on (Cartech, Bell, Vortech, etc) RRFPR. You need to have a FPR that sets a base pressure for those types of RRFPR's to run off of. You can remove the stock FPR only when you put another FPR in it's place that has the ability to run a base fuel pressure. The add-on regulators just add pressure onto what the existing pressure is in the lines.
Say a FPR is set to run 34psi with the return line back to the tank running 1psi (for example). When you put an add-on RRFPR in line, you set it so that it rises at 1psi at whatever rate. What it in effect does is add pressure between the return of the FPR and the RRFPR. The FPR "adjusts" for the pressure difference by rising the rate in the line going past the injectors into the FPR. The more pressure in the line between the FPR and RRFPR, the higher the pressure in the injector section of line is.