My 07 F250 Superduty 5.4 has 150k on it. I recently replaced the passenger exhaust manifold as it had cracked. The driver side is now sounding like it has a leak. Is it common for one side to leak after replacing the other with this high mileage? I also noticed that the new gasket that came with the pass. manifold kit was 3 ply compared to the factory 1 ply. Could this also be a symptom of clogging cats? Thank you for your time.