How can you tell the difference between an exhaust header gasket leak and a valve tick?

After rebuild I have a tick, worse when the engine is cold but still there when warm. Right hand bank only.

Builder thinks its the header gasket leak, but I replaced the gasket and its still there. The gasket I took out didn't have any obvious cracks or blow outs.

I tried adjusting the valves (hydraulic lifters), engine off, and it didn't help. Haven't yet tried to adjust them with engine running.

Hate to ask the next question, but how do you know if you have a cam lobe flat spot tick?