Q&A

 Master

BMW blamed lifter failure on infrequent oil changes. A good low viscosity engine oil with good detergentcy package is good. Have you tried using Risolene oil additive it is low viscosity high detergentcy and cleans lifters, I used it on my VWs and some customers Isuzus. Try that first maybe with synthetic oil of the lowest viscosity called for in your owners manual and see if the lifters "clean out".
Replacing the lifters is not a job to be taken on at home I think it is 7 hour job. Look up Alldata and see the instructions it is complex and may require special tools.