You wont see much gain from just a filter on a diesel. The fuel pump tweek is a good mod if you want a bit more go as is changing the intercooler as the standard one is quite restrictive I think.
 
I have an auto so i dont think the pump is that easy to mod. I am not really wanting more power to be honest just curious.
I altered the pump timing the other day as it was getting hard to start and that made a massive improvement.
I have wondered if its and advantage to shorted the turbo waste gate a tad.
 

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