It goes like this: "my dad is a cop"
I haven't ever had a problem with Subaru exhaust tone, but for the year or so that I drove a CRX it seemed like I was always getting pulled over for exhaust, and it was stock! I think that the lower "broken V8" tone is more discrete and less penetrating than the weedwhacker whine, and that's why cops don't pay as much attention to it.
Sorry about the tangent, it does suck to be hastled for no reason by people who are supposed to be "protecting and serving"

At least you didn't get ticketed.