There are other posts in here with the same problem. Do not be surprised if it comes back in 6 months.
I have been lucky enough not to have this problem yet. knock on wood.
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2000 Silverado Z71, 5.3L, K&N GenII Air Intake, Y-pipe Exhaust (no muffler), Bosch Platnium +4 plugs, 242k miles and still running.