1996 Chevy Lumina Ticking noise from top of engine with los

My husband bought a 96 Lumina about 3 weeks ago. There was an Intake Mainfold leak, which was under warrenty so we had it fixed last week. About 2 days later, a ticking noise came out of the top of the engine with loss of power to the gas. We left the car sit for 1 day, then this morning he took it to a garage, which told him a sticky valve. The power came back, and now drives o.K but the ticking sound is still there. Could this be a cause of the 3 coils not being placed back properly when the Manifold Gasket was replaced? Or could there be something seriously wrong. The check engine light doesn't come on at all and the temp is fine. There is no miss fire or back fire happening either. Thank you.