just removed and serviced injectors and did a valve job. The car was just running after a drive and I was poking my head around under the hood to make sure everything looked and sounded good and I noticed a faint tapping sound through the header that sounded between cylinder 1 and 2 on the exhaust side. very very faint. I put my ear up to the valve cover and that sounded clean. is it normal to get some slight tapping sounds that can be heard through the exhaust? between 1 and 2 just stood out to me.