I just use copper slip for mine.
Not sure if it's best for long term use but I tend to strip mine once a year so it works for me.
Creedxup used to sell the proper grease for the job, not sure if he still does but I'm sure he will be along soon to put me right.
I have found any grease only attracts the soot and turns into sticky black crap..i fit them dry...the soot is lubrication thats how variable vane geometry turbos lubricate themselves...
As soon as you introduce oil or grease then they collect it and jam.
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The manual states that 'Molybdenum disulphide grease should be used, but bostik never seez is better, I have a spare kicking about if you want to buy a tin ?