For those that don't know the 1UZ does not run conventional lifters (like hydraulic lifters)
People may have heard them being called shims and buckets.
In the 1UZ the bucket goes on the valve, and then the shim sits between the bucket and the cam.
At high rpm/high ramp/high lift this shim has a tendency to be dislodged/spat out.
So you need to do a shim UNDER bucket conversion. (ie shim goes between the bucket and the valve.
Now, with the 1NZFE motor, they run SHIMLESS buckets, ie the bucket IS the shim as well. Obviously it will be much harder to spit one of these out.
They are available for about $10aud each if you know the right people.