I have sort of the same problem. My 09 aveo roars when I push the gas pedal but doesn't accelerate in accordance with how hard I push on the pedal. It stutters sometimes but not always. But I haven't experienced a smell, but I have a strong air freshener. Last year they put in a new drive-shaft (I think that's what it's called) and It performed better than when I bought it. It's slowly getting worse performance but all checks out with the service dept. at my local chevy dealer.