[tonythetarga]

Typically, piston slap is due to wear and doesn’t come and go.
If you’re concerned about your cylinders, get them borascoped.
When I take my Cayman out of storage it needs to run until operating temp first. I may get codes after disconnecting the battery for 6 months, but once it runs, warms up at idle and then starts again later, any connection/sensor etc issue is fine.
If your noise comes back, try and isolate it with the ac off and see if it’s engine, alternator, air pump, water pump etc. lots of things running at the same time.