I am currently going through the same problem since 9k miles now at 18k. Ticking noise while under load at low rpms. Had it in the shop 3 times so far goes back this Monday for round 4. 1st time they said couldn't replicate, 2nd time blamed K&N cai 3rd time I removed cai and they finally heard the noise and said it's not normal. Tech intially thought exhaust leak but none found.They called GM engineer who suggested vacuum pump replacement. Still ticking. I feel like it's the coming from catalytic converter, maybe internal crack? Let's see what they do next.
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