you refering to a nitrous "push" system? the CT racing pro mods (Chuck, Jason, Chad Peterson's chevelles) ran this type of system when running their nitrous setup before switching to blower engines. Utilizing a regulated CO2 bottle plummed into the nitrous bottle valve, it allowed for more consistant bottle pressures without having to heat or cool bottles. Plus as bottle would empty and pressure dropped the nitrous would boil inside the bottle and this system eliminated that problem.
I havent heard of alot of people still running the system. Surely somebody out there is still running it. I plan on running the setup if/when i get nitrous setup to run top dragster on my 605 bbc.