This is commom problem on higher mileage M113 engine which is what you have. How many on your car so far?
Also have you been changing the oil regulary, and used synthetic oil?
A while back I had a E430 with the lifter noise you describe. The only times I was able to lower the ticking noise is when I did two things: use high octange gase at least 91 and add 1 qt of Marvel Mystery Oil to the engine.