I have a '74 02 and when I am braking sometimes I lose the pedal usually after coasting and the pedal returns with 1 pump of the brake pedal there is no fluid loss but this started after giving the car a tune up. I'm thinking the idle might be too low. Any suggestions would be great. Thank you

Do you actually lose the pedal as in loosing the brakes altoghter or does it become harder to actuate the brakes? If it is harder to actuate the brakes, something is affecting the brake booster. If you are losing brakes altogther, do not drive until problem is fixed.
First check your brake booster vacuum line. It should go from a full vacuum manifold port to the brake booster. It should also have a one way valve in this line (looks like a PCV valve but isn't). The black part should be closest to the manifold. The valve is designed to trap vacuum in the booster. Make sure the valve is not malfuctioning by checking the opening and closing of it. If this is intact, you need to pull a vacuum on the vacuum line and brake booster to check for a leak in the booster itself.