There is a TSB issued by chevy. Google chevy 6.2 liter valve spring issues. There's a bad batch of springs. Not a recall YET but should be. Not sure if you can search by vin. If posted in "trail boss not" post. Mine was in/out of shop at 600 miles blown cylinder 3. I was devastated. Repaired in 24 hours, replaced all valve springs. Guaranteed it with 100,000 mile warranty on motor (transferable). Not happy with the problem but they fixed it and backed it up. Turned 4000 miles today. I run it hard and its ...... well..... like it should have been new.
Full disclosure, I didn't give a true break in period for my 6.2, just had to feel that horsepower, which I NOW recommend. Good luck, love my TB.