yup twitch has it. same thing was happening to me. a regulator will fix it, or like fadedawg might have mentioned, a cold trap. or putting the valve closer to the vacuum pump, and not right on the chamber.. or have 2, and just add another right after the vacuum pump, before the hose starts. vacuum pump - ball valve - hose - ball valve - relief valve - vac chamber.
try not to position your oil directly under the air inlet thing in the lid.
AND, when youre done sucking on the chamber and gonna let it sit, after you close the ball valve, unscrew the hose from the vacuum pump. it lets the hose equalize in pressure. then hook it back up for future use. problem solved. 0$ spent.
twich, that regulator looks cheap, no offense... where did ya get it? how much was it? id get one if it was the right price.