Bob, I had terrible lifter clatter when I first bought my 5kcstq as well.
It can be easily solved by using the factory oil filters, and synthetic oil
isn't a bad idea as well. This solved my problem. 1-2 seconds on start up
is normal.
As far as oil additives. I've had good experience with Marvel Mystery
Oil and MOA (if you can find it). Got mine from a BMW tech.
Later,
Dan