If it sticks when your foot isn't on the gas and you have to apply more pressure to get it to unstick to move the vehicle, it might be carbon buildup in the throttle body. This happened in my mini. The quick & dirty fix is to remove the hose from the air mass filter to the throttle body on the TB end, shoot a bunch of carburetor cleaner in there and use a wire brush to brush out the gunk, making sure to get around the flap in there. Reconnect the hose, start up the engine. It'll sound terrible for the first 30 sec until the carburetor cleaner burns up. The longer term fix is to remove the TB and soak it in carburetor cleaner.