Manifold/header/muffler/tail Pipe problems of the 2004 Nissan Pathfinder

I am the owner of a 2004 Pathfinder with 79,000miles. I was driving on June 6th when my engine began to produce a loud knock. I immediately pulled over and called a tow truck. I had the vehicle towed home so I could investigate the noise. Upon removal of the upper intake manifold I found 1 of the 6 power valves had moved from its proper location, and was on top of another valve. The 2 screws meant to hold it in place were missing, and I found that 8 of the 10 remaining screws to be loose. I was able to find 1 screw that was sitting down inside the head, about to enter the cylinder. I then preceded to remove each screw, locked it, and reinstall it. Hoping this solved the problem, I reassembled the engine, and started it. The knock was still there. So this means that the screw I couldn't find made its way into the cylinder and caused unknown damage. A simple internet search will find numerous reports of this happening on altimas, sentras, and Pathfinders because the screws were not properly locked at the factory, making this a manufacturers defect. Something that should have been dealt with by issuing a mandatory service, there by not wasting my time and money on something that takes less than an hour to remedy. My vehicle is currently undrivable for fear of further damage, as I await a response from Nissan north America on what action, if any, they will do to investigate.

2004 Nissan Pathfinder with service engine light on. Consumer states that the vehicle had smoke coming from the tail pipe, losing power and wouldn't go over 45 mph. Mechanic stated the vehicle was 4 quarts low on oil. The consumer stated the oil had been changed on Feb 2, 2008. And on April 3, 2008 the consumer was informed the vehicle needed a new engine. The consumer stated it was the dealers fault that the engine needed to be replaced. She believed they failed to put in new oil on the last visit.