Dodge/Cummins 94>98 vintage with an inline injector pump, had a campaign to up date the return springs. If memory serves , they may have installed dual springs.
They also had problems with the throttle stop wearing into the linkage, causing an erratic idle speed.
I'll see if I can find info on the spring P/N .
Any chance you can post a picture of your linkage so I can tell you if what you have is the same as the pick-up trucks.