Yeah Port Byron, I guess it's not really Northern Illinois, it's Northwestern. It's close to the quad cities and on the mississippi. Byron is a ways away. Look it up on mapquest or expedia.
The address of the place is going to be close to 831 N High Street (IL-84) Port Byron, IL 61275
the 831 is a rough guess.
Edit: Sorry on the Name, it's call Illinois Dyno Centerhttp://www.powercommander.com/opccidc.shtml is a website with some of their contact info.