Fuel pump diapragm

Hi all, ive just purchased another 200tdi 90 as a project.
Ive had a quick look at the injector pump as it was standard tune and felt really sluggish at the side of my tweaked 90, I removed the four screws on the top of the pump so I could rotate the plunger to give it abit more fuel on boost and I found it had a anodised blue spring fitted.
Is this a aftermarket part?

I removed the spring from my other 90 and the poundage is alot less and the other spring is steel not alloy, the engine in my new 90 is a disco lump where as my other one is a defender lump.

I fitted the blue spring to my tweaked 90 (defender engine) which I use as a everyday car and now it gives alot of black smoke out just as its coming onto boost rather than just abit. It still goes like stink tho!!

Has anybody come across the blue ally spring before in a 200tdi pump?

Yes mate I also have blue springs in two different inj pumps on different engines and I've seen many other blue springs fitted to disco and defender200 tdi you need a manometer to test the strength of a spring !! Black smoke usually means you have tweaked it just a bit too much ! Try backing off the full power adjuster on inj pump , it'll make massive changes with just a tiny adjustment !!

Thanks for that i'll give it a go, I turned the smoke control screw half a turn out and its not smoking as bad now.