normally you need spacers in their to get better milage

Have you changed anything, or did something change itself?

As Gort says, learn to read the color of the spark plug.
http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

With your "stage 1 kit" you can try turning the idle adjustment screw in (clockwise) as far as possible without hurting engine performance.  You can try lifting the jet needle less by adding a 3mm washer (about .5mm thick) or two on top of the thin kit spacer, again as much as possible without hurting performance.

Unlike a post-'86 car with a mass airflow sensor and other electronic controls, our motorcycle fuel system is primitive.  A dirty air filter element will cause rich operation.  If your K&N element looks like a lint blanket, it needs cleaning & re-oiling.  A $15 HiFlo brand replacement from a non-Suzuki shop is a good choice if needed for those with a dirty stock air filter.

If you changed anything, retrace your steps; maybe you did something that caused the problem.

What did you tell them to do?

check your plug, then if out of whack take it back.

aside from that, drop the bowl, see if the jets are in the bowl.

How many disks did they install?

Now, that's sooty black! Carbon deposits on the plug = mixture too rich.