2000 Chevrolet , misfire on #5 cylinder,see details?

Drove to job (72 miles) everything fine ,got back in truck that afternoon, seemed like a dead miss, stopped at Advance Auto, they tested said it was EGR valve, mechanic replaced this and it's still missing on #5 cyl., ran compression test, 3 cylinders including #5 were 71%,the rest are 75%, replaced all spark plugs, but no improvement, please help, could this be a failed power pac at that cyl. or maybe a injector, i just don't know with these newer vehicles, used to working on the 1975 and before models, also this is a 5.7 liter V8, went back to Advance Auto and it shows multiple misfires on their tester