My 93 SC400 has the classice driver side lifter tic. I have tried everything in a bottle, SeaFoam, STP Engine treat ment. I use synthetic 5w 30 oil and also tried 10w 30 synthetic but the tic remains. The oil coming out at oil change is really clean so I don't suspect sludge buildup.

Any suggestions for a remedy?

Also if I pulled the valve cover off to expose the lifters do you think I could clean the lifters enough to fix this issue?