2001 grand prix gtp 3800 II supercharged. i just replaced my LIM gastket and the upper plenium. Ive checked all my vacuum lines and did vacuum leak tests but cant figure out why my car is idling so rough. it throws a code for vacuum volume i believe and i noticed that there were black specks in the snow outside of garage when i run it which i am assuming is oil. checked my oil and it was 3 quarts low. please help!