i jus bought a mercedes 500sel and the gas mileage was very bad i didnt know the problem so i left it alone and yesterday i took off the air filter housing and it was filled with sand and dirt and the air filters were shot and black,so i cleaned it out and bought new air filters and the gas mileage is so much better but now when i start it the idle bounces around 5 and 10 and when im stopped at a red light,also there is a loud sucking sound when i open the hood and now the whole engine sounds different