I'm getting ready to install my magnaflow x pipe on my 99 GT. The one thing I need to know those that have done an H pipe swap on a 99+ Mustang did you change out the passenger side gasket or did you reuse the old one???
Nah, I never had any problems. I would just do it for peace of mind. I doubt you would have any problems with it unless the gasket is chewed up. You should be alright.