rough idle...valves?

will valve cleaners (fuel additives) help improve a rough idle? feels like i have a vacuum leak or bad valve...loss of power, bad mileage, rhythmic pressure from tailpipe...any advice?

Maybe a little help if injectors clogging. What year, engine, etc? Many different causes such as IAC valve, dirty intake, plugs, wires, filters (both gas and air) and even air filter intakes(cracked or split hoses) and vacuum leaks will cause this. Would not hurt to run some injector cleaner anyway, most likely a Techron type just to help clean the injectors a bit.

Look at your plugs?

Any mechanical noise in the motor? Might have a rocker arm loose or something also.

That was one nice thing about carbed engines. If you suspected a vacuum leak, you'd just partially choke it with your hand, if it started running better, you knew you were right.