My VW repair manual has a nice procedure for testing hydro. lifters:

4. Cylinder Head - 4.6 Hydraulic Cam Followers - Checking Hydraulic Cam Followers

That said with all the bother of taking the chain apart I'd want to replace all the lifters if I was that far into it. It's too bad the Mercedes lifters cost 2x what VW ones do

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.