91 Cavalier V6 problems

I have two problems with my 1991 Cavalier 3.1;
if I don't disconnect the battery evry time the car is not in use it will go dead after a three days, the battery is brand new so I know it isn't the battery. Also when I stop my car completely and shift from drive to reverse, the car quits, it only stays runnign if i rev it

do you have an after market radio

I have 4 cavailers z24s try in the trunk there is a light unplug it and the glove box there is one and under the hood try that

2 problem under the hood on auto trannys under the breather is a plug it should be blue with 4 wires maybe 3 or 2 wires unplug it
it is call tcc swicth they all ways go try it

do you have anything aftermarket hooked up to the battery, whether it be a stereo, or stereo components, or special lights or anything you installed?