If you take route 9 west from BU, turn left onto Lee St (right before Chestnut Hill Ave) and take a left onto Newton St and a left onto Goddard Ave, it's a short but very twisty road that leads you to the jamaicaway. Goddard itself it at max like a mile long, but there's a couple of good scary blind corners. It's my stress relief road. Be warned though, run it late at night or it'll either be crawling with cops or motorists.
Another road I've found is Chickatawbut Road in Milton. Take 93S from Boston to exit 5B and take the right at the railroad track. I think it's a good 2 or 3 miles long and it's fast. It's full of sweeping corners that you can take at 80+ if you have the balls. My senior year of high school, we crashed my friend's 318ti on the cambered left after the bridge. Cops came and we were like "a deer ran out in to the road".
Other than that, Boston's really a congested hellhole to drive in and it's tough to find a nice empty road to let loose.
Hope you guys have fun.