I recently purchased a 1996 w210 e320 with the m104 engine. After the car had been sitting for about a month, i tried starting it up but the battery was flat. When i gave the car a jump and got it going, the idle was very smooth and at the normal rpm range, but whenever I tried revving the car in park it would sound like it was drowning and wouldnt go above 2500 rpm. With the throttle completely depressed, it would be bouncing between 2000 and 2500 rpm. When drive was engaged the car would be bouncing between 500 and 1000 rpm when creeping and would have almost no power upon acceleration. When I attempted going up a small hill, the car stalled. The car smells like it is running very rich, but the maf and the o2 sensors are almost brand new. Could this just be the battery? Any suggestions?