Getting ready to change filters on the truck and was waiting for this to install the tuning kit spring and shims. It's set at 18psi now, what shims in addition to the heavier spring will get me to 25psi? How about 30 psi? Thanks

 

The instructions on the kit are pretty clear. I am doing this from memory so I will be wrong but I'll do my best. First note direction of the return valve (the "T" points to the fuel tank) Unscrew the valve. Note where the spring is and note where the shims are. You will install the new stuff the same way... this is important! The shims go to the bottom of the small end piece of the valve and you put the spring on top. I think the new heavier spring with one of the small shims will get you 24-25 psi. Add one of the thick shims (one that you took out originally) in addition to the spring and small shim and that will get you close to 30. I am running at 32. It is best to have calipers to measure the actual shim thickness you are using. I don't want to use the thickness as I don't remember honestly-- I want to say it was .110 for me to get 32 psi.
I recommend you start small, put it together, check pressure and if you want more, add a small shim at a time until you get what you want.

 

I only wanted to do it once instead of assembling/disassembling. I know how to put it together, just don't know which combo will get me 25 or 30 psi. I ordered the tuning kit and there were no directions that tell you which combo and their respective psi.