Right now i live at 4500 ft asl but race at sea level, how much change am i going to see in IDC from the elevation drop?

 

the airmass will change, fuel trims will change, not sure how much exactly your IDC will change, probably minimal. You can lookup the airmass tables based on elevation and see the difference. not quite sure about calculating how much it would change it.

 

air density will change, likely your IDC will go up ever so slightly, you may not even see a change in it, but will see a change in fuel trims

 

The duty cycle should increase proportionally with the air density as you go towards sea level.

All other things being constant, you would change about 4-4.5% per 1000ft.
In your case, 18% would be a decent guess.