Shim Kit?

[trgoffroader7]

Ive got a 05 lly duramax. I installed the shim kit but was wondering wat does it actually do or how does it work? Just put more pressure on the valve for higher fuel pressure? and if I were to remove the puck does the shim kit need to be removed as well? Im thinking of removing puck bc before installed I was getting 15 to 16 mpg and with it installed ive been getting 13 regularly whether i baby the throttle or not.

[mikel]

It keeps the relief valve from dumping the extra pressure created by the puck.

You can leave the shim kit installed without the puck.