I could see it both ways. Doing a quick Google search I see plenty of companies offering stacks for sale in Michigan.

I bet it has to do with how tall they are. A couple years back I saw a Class 8 semi with HUGE Stacks, like borderline they could even fit under an overpass. It was ridiculous.

Josh

 

The Dodge Lil Red may have been an exception because its stacks were stock too. The law could be against aftermarket ones.

 

I cant think of a reason why stacks would even be illegal.

 

5" stacks on my 65' f100.

 

Well here is a FTE buds truck (small pic lower right) and my mudder with Hedman headers straight to stacks.

Loud and obnoxious......if you do not like stacks, looks the other way and just don't put them on YOUR rig.