I resetted my ECU 2nd time a few weeks ago. It does make a difference if you put new mods on your car. This should remap it according to your new mods. Experience i had was from a standard turbo back zorst to a 3" turbo back. Without resetting my ECU on idle, it jumps from time to time. Now that i resetted it, it fixed itself and the idle now runs alot smoother.