The way to find exhaust leaks is with a piece of hose, anything from fuel line to heater hose. Hold one end near your ear but start with maybe 2" away. Probe around and area. Move closer to your ear. Probe again, etc. You'll find it if it's exhaust.
Sometimes you can hear other noise, lifter, etc, same way.
Find out if it's "hitting" on all holes. DO NOT pull plug wires off as other people claim. This causes a crossfire situation, and can damage electronics as well as "carbon track" the cap/ rotor. Instead, pull the dist. boots loose, gently work small brads, paper clips etc, down beside each wire, and use a probe --screwdrive with a ground clip wire--to short out each cylinder. Do this at "best smooth idle"