Why does my Z die at an Idle ?

[Sb_75_280z]

Im new to this site and am looking for answers , I have a 75 280z thats mosty stock other than this aftermarket air filter that the owner before the owner I bought it from installed , anyways My car wants to die at an idle and runs a little rough , Ive had the car since February and have replaced the gas tank , fuel pump , fuel filter and battery since then , 
the car sometimes makes a clicking sound that seems to be coming from the Dash , My dad and I took out the alternator and cleaned it up but its still not putting out enough power and the lights dim at low rpms , anyways I feel as if the car is starving for air and that the reason might be a vaccum leak of some kind but I honestly wouldnt know if thats the only problem , anyways please help 

thanks