tapping noise

[Fastshivy]

Ok 2018 Tahoe 5.3 When you accelerate there is an intermittent tapping noise coming from the driver side (engine bay??). The dealer replaced the muffler and checked the cat and exhaust manifold bolts...It is still there but not quite as loud...Any help would be appreciated. They are stumped. It sounds like a wood pecker beating on an old hard tree.