I also work for Nissan and we see so many headgaskets, throttle chambers, crank sensors, fuel pumps, and cats go bad. We also see the powervalve screws come apart and take the motor out. But the worst thing about that motor, is that we see a lot of oil consumption. A couple of years they were produced with bad piston rings and they burnt oil. They have a recall to test the crank case pressure, to determine if the motor needs to be replaced. Since then they have worked out that problem on the new qr25's. I have seen at least 5 Altimas throw rods out the block due to oil loss. I honestly hate that motor.