If that engine was burning oil for a long time, chances are the cat is trashed. Are you smelling sulphur dioxide.... rotten eggs?

BTW, I think your engine may have VLAs (valve lash adjusters). If so and if it's tapping, there's a trick to calm them down:

From idle, slowly and steadily rev the engine to 3,000 rpm over a period of 15 seconds. Then let it idle for 15 seconds. Repeat the cycle up to 20 times. Usually they'll calm down after only a few cycles.

Frank