Have you ridden the Westside of the MI? M25 in the thumb is a fairly boring ride, M23 north is better but both pale in comparison to M22 on the West side. Ride M25 if you want to try it once, then pick up Highway 10 near Bay City over to the west side. Take 31 into Manistee where you can pick up M22 north. Lots of winding twisty roads with small tourist towns and parks. Take M22 all the way to North Port at the top of Leelanau Peninsula and back down into Traverse City. Then run 31 north to Charlevoix, Petoskey and pick up M119 (also know as the tunnel of trees) to get to Mackinaw. Can easily spend a few days finding great food and sight seeing and fun roads to rind in the TC and Petoskey area.
If you stay the East rout, there is the little town of Frankenmuth just south of Saginaw. It is a Christmas store shopping meca, not my thing but many like it. it. There are the Thumb brewery and Frankenmuth brewery, both are decent but much better to be had in MI. Along M23 Wiltse's in Oscoda, is a good lunch/dinner stop, they have awesome pulled pork.
As others have mentioned H58 in the UP between Munising and Grand Marias is a must ride. The Superior Brewing Co in Grand Marias is a great lunch stop, if you can get in. During the summer season plan for a wait.