What's its purpose and is it a problem that my car will start and run with it disconnected?
Thanks guys.

The yellow wire bypasses the ballast resistor while the starter is engaged. It was meant to provide a hotter spark during the start cycle. If your setup works well without it you have no need for it.

The yellow wire bypasses the ballast resistor while the starter is engaged. It was meant to provide a hotter spark during the start cycle. If your setup works well without it you have no need for it.

Cool, I won't worry about it then. Thanks.