My 02 LS1 Camaro has done it since new. Meh, 10 years later it still runs great & turns 13.7 @ 103 at the track, not bad for a heavier drop top. I know it's an annoying sound, but I wouldn't worry about it. I also wouldn't mess around with additives. I run Mobil 1 5W30, no issues or leaks since new. Run the same in my 94 LT1. It's quite on start up. My 5.3L in my Avalanche is quiet.