Going about 120kph (@ 80 mph) and lifting off the gas produced a noticable hum/vibration that was not there before. I had service done to the car yesterday (rear brakes, fluids etc.) and everything seemed fine, though I'd not had it going fast. When I came home I torqued the bolts again and though 1 or 2 had a little room to turn them up to 80 lbs/feet (like 1/10th rotation, real small) it does not seem enough out to have caused this. I checked the FAQs but could not find any mention of vibration issues. The car handles fine and in all ways seems good but this vibe's got me concerned. It's a 1991, incidently. Any thoughts?