Funny noise from right front of vehicle...

[87iroc]

My wife and I took our first long trip in the Vibe last week. Car did great, but on the way home, a noise developed in the right front-ish side of the vehicle.It's hard to describe, but it almost sounded like a slight exhaust leak. It only appeared as the vehicle would accelerate up a hill...and it would stop if we were going downhill. Now the wife is able to recreate it by just accelerating.My wife got rear-ended in the car a few days after we got it and they replaced the exhaust...but I am wondering if it is maybe a cracked exhaust manifold that just appeared from that incident...Has anyone else had weird noises similar to this coming from the vehicle during acceleration or when the engine is under load? I wish I could describe the noise...but I can't come up with words...other than it sounding like a exhaust leak...but much quicker than any I have ever heard.(Asking this in case it is a normal vibe thing and not from the accident.) The accident was 8 months ago now...Thanks,