When I changed the PS pump on my 00 K3500 I got a remanufactured one from the local parts store. The old one had that little EVO valve. The new one just said to remove that portion and tape the wire connector back. I was puzzled what the heck that thing was, as I had never seen it before.
It was months later I read here about the EVO thing, LOL. I can't say I felt any difference before or after. Don't even know if it was working before, LOL.
Interestingly, some of the early GMT800 trucks apparently had it, perhaps 99-02, not sure. On my 99 Silverado I'm doing an engine swap there are some pins on the engine wiring harness that say something EVO, but mine are empty and doesn't have EVO.
I thought that EVO thing was meant for a more nimble feeling at low speed, more tailored to soccer Moms driving SUVs? Or so I read here. Don't know why any 2500/3500 truck would have it or need one?