Gov spring kit
#4
If you are driving an auto, it is most likely going to want to shift at or around 3K, the only advantage to you in an auto that I have seen with the 4K spring is that you know you will have full fuel up to the point the transmission will want to shift, where as the 3K gsk will be out of fuel just before that point. I love the 4k in my manual as it allows me to run a little further into RPM in a lower gear while towing to keep momentum on hills etc.