Manifold/header/muffler/tail Pipe problems of the 2008 Nissan Xterra

Less than 45,000 miles on the vehicle, no engine lights were on and no other issues prior to the incident. Traveling on i75 at about 65mph when the vehicle suddenly and rapidly slows down and almost caused an accident. Got to the side of the road and tried to accelerate, the vehicle would only go about 25-30mph so I had it towed home. I later had it towed to the dealer and paid for a diagnosis, the service tech said an aftermarket mass airflow sensor caused the all the catalytic converters to go bad and they wanted $3,500 to replace the catalytic converters and exhaust manifolds before they would continue diagnosing the vehicle. I called my sae certified mechanic and had it towed to him. He said the mass airflow sensor was the factory sensor that came on the car, and shouldn't have caused a failure in the catalytic converters especially without a check engine light. He said that Nissan has had problems with catalytic converters going bad and causing engine failure, so upon further inspection the engine has damage to the cylinders and valves and will need replaced or at least overhauled. I don't believe I should have to pay for an engine and catalytic converters that could have been replaced with a recall and prevented the entire issue. Nissan has an internal bulletin about the catalytic converter failures and engine damage proving they had prior knowledge of the issues including issues with the timing chains that fail which is another issue with this engine that I haven't come across yet.