Why does my car stall when i take my foot off the gas pedal? on 2002 Cadillac DeVille

the car starts right up. But when i put my foot on the brake to put it in gear it cuts off.

Asked by for the 2002 Cadillac DeVille
You may have a hole in the brake booster rubber diaphragm. It will be exposed to air when you step on the brake, which causes a huge vacuum leak and then your engine dies. This is where I would start.