2003 Mercedes-Benz SLK-Class - Lifter Tap

when the roof is up I hear a lifter tap between 1000-2500 rpm when the roof is down the sound goes away

Do you mean the engine lifter? If so there are probably hydraulic valve clearance compensation elements available that will correct that. Make sure the engine oil is in good condition & the level is correct of course.

Could be purge valve. Behind washer bottle. Makes a ticking sound. From MB website.

The road noise probably drowns out the ticking when to top is down.