i had monroe add my h pipe to my 95 gt they took about an hour to install it. when the started up the car sounded mean as hell intul i drove down the road, then it sounded like i had a helicopter under my hood. so there must be a leak somewhere but iw atched him tighten everything up. could the leak be at the header to h pipe or maybe on the 02 sensors the right one had to be welded to stay in place? any help woould be great.