Join Date: May 2005
Location: Mayenne France
My Motorhome: Pilote 733 FJ
Thanked 193 Times in 170 Posts
I've not researched it but are figures available for the expected results from a prescribed test of the returns?
If they are it will give you a definite answer to your question.
As your problem is white smoke which would suggest excess unburnt diesel, maybe 2 is the culprit, although only 1 and 4 look similar, possibly 3 is the only one working to specification.
Very difficult to make proper informed suggestions as the operation of the injection system is rather complex, not just the mechanical operation of the injectors themselves.