2000 Ford Windstar OBD code for cyl 3 misfiring, EGR valve

2000 Ford Windstar 6 cyl 165000 miles

Hi,
I have a cyl 3 misfire, egr valve, and lean fuel mixture codes. I have canged the egr valve but that did not fix it. I was told by the inspection station that it could be a vaccum leak, and I do here a sucking noise for a second when I rev it up, but the guy said all ford v6's make that quick sucking noise. How can I check for a vaccum leak? I am also going to check the coil when I get home tonight but I am not sure wich cyl is #3. Can anyone elp me I have been trying to figure this out for weeks.