Originally Posted by JFUSION

Remove the plastic fuel rail cover. Get a bright flashlight and pressurize the fuel system by turning on the ignition, and check around under and around the intake manifold and fuel hose area. You don't have to start the car at this point. Your nose might lead you to the right location, lol. Look for light moisture around all of the fuel related parts, you probably won't see large drops of fuel, it's going to be a very fine amount of fuel spraying or oozing out from one of the parts. The fuel hose that mounts under the fuel pulsation dampener has a joint in it about 6 inches below the intake manifold, that would be a good spot to check, you need to look down between the intake manifold runners with a bright light shining on the metal portion of that hose.

Good luck.

Originally Posted by Billman250

Also check for loose spark plugs.

I had a customer complain of the same thing and it was loose plugs.