Vauxhall Corsa car loosing power holds back and loud

hi car was running good this morning went to petrol station put 10 pounds of petrol in thene go back home running good couple of hours later go out again and car was louder kind of vibrates can still drive it but not much power in it whene driving thought there might of been a hole in exhaust but checked it could not see eny maybe a faulty airflow metre dont know if it would make car sound louder and vibrate a bit more and kind of holds back a bit whene driving any suggestions would be appreciated i will give exhaust another look over at manafold to back pipe incase i missed eny THANKS