My Honda CRV EX is very loud both under acceleration and if I pull my foot off the gas at highway speeds - sounds like a turbo whine constantly. If I idle or am parked and rev the engine, there is no whine. I looked over the exhaust and didn't see any rusted holes, plus I would think that revving the engine in park would produce same noise level, but it doesn't - only when going above maybe 50. Any ideas?