I picked up one at the local hardware store (stock on left, new spring on the right):

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[Linked Image]

[Linked Image]

I can supply one if you can't find one locally. Yes, does stiffen up the gas pedal a little but I find that helps off-road. Makes it less likely that you blip the throttle going over bumps. I also adjust the dash pot plunger spring to help lift the throttle linkage off idle.