I've taken mine off, cleaned the little mesh grille, inspected it, etc. I'm still have a jumping idle when the motor is cold and the clutch is out.

Question is, do they go bad aside from what I could visually see? Is there something else that could be causing the issue?

 

Yes, the seals go bad over time.

Try bleeding the coolant before you replace the IACV.

 

Done that too. I just read a thread explaining some dynamic vacuum leak (FIT) on the throttle body, gonna try that tomorrow).