[shorod]

Welcome to the forum!

Your issue certainly sounds like another cylinder misfire and leaky valve cover gasket. Was the valve cover gasket only replace on one side?

Many of the chain auto parts stores will read trouble codes at no charge. However, not all of the tools they use are scan tools, some are just code readers. If you can find one that uses a scan tool with the ability to retrieve "Component Parameters" or PIDs, check the misfire counts on the 8 cylinders. You may find high counts on one or more cylinders, but not high enough to set a check engine light.

The "exhaust" smell you reference is likely oil leaking from the valve cover onto the exhaust manifold. The gasket is probably also leaking oil into the spark plug wells causing a coil to short through the oil to the cylinder head, which causes a cylinder misfire.

-Rod