96 Cavalier, 2.2 149 000 Km

RE: I hear a ratling in my back end from both shocks.

Do you have the stock struts on that car.

My guess would be you have wornout strut bushings & bearing mounts.

RE: having trouble getting my motor to idle over 600 rpm without having it go up over 1000 rpm.

Do u have a check egine light on, Have you checkout youre throttle body see if it clean. Could have a carboned throttle body, Or dirty IAC sensor. Need to be cleaned with car Or throttle body cleaner.
If that doesnt correct it they u need to check for vacuum leak in a hose or something.

Good Luck.