Test hose is the only way. I made mine out of spare parts, there's a thread on here somewhere that gives actual part numbers if you dont have spare stuff laying around
I made a test hose for the RFI. The 2003 RFI has a port/Tee in the line but it's kinda strange. No schrader valve. I just glanced at it and knew my gauge line wouldn't work. I'll post a picture when I have time.