Not having a tank or some sort of resevoir such as a section tube/pipe the regulator cannot do its job adequately. The compressor is constantly pulsing the air pressure as it pushes it out the outlet. A tank not only acts as a resevoir but as a baffle to absorb the pulsing. The regulator can then control the airflow by controlling the volume at which it exits the tank. I've also had some luck using a large glass bowl moisture trap in line between the compressor and the regulator.
Two features I look for in a regulator, a guage that reads accurately the pressure ranges I use for airbrushing and a control that allows adjustments by the 1/2 pound at the most...jumping a couple of pounds with the slightest adjustment just doesn't cut it for me.