I was reading on citydiesel.net that it gives 50-100 HP...I can see that maybe in the top end where you won't be fighting the fuel cutoff that starts with the stock governor springs but does it give more power throwout the rpm range?

 

Only on the top end like you thought. I don't see how it would affect anything under about 2500 rpm.

 

A GSK gives you more usable hp.
Without the GSK your higher rpms are basically useless.

 

I installed mine along with a #10 plate so I'm not sure what the GSK by itself did but the two of them together made it feel like a whole new truck.

 

the 3k gsk is the best thing we ever did to my dadsa truck. almost 80 out of od

 

You will make more power down low also. Mostly more usable power up top but the GSK does affect the govenor at lower speeds. My 3GSK fuels hard to about 2500RPM then starts the downhill slide. I need to put the 4k spring back in.

 

If you are going for dyno numbers, the 3k GSK won't make a ton of difference. However, it does make a lot of difference when towing. It gives you a wider usable rpm range which means that you can enter the next gear at a higher rpm. Putting one in will allow upshifts on hills where you previously could not.

 

Very good point.