Dad's 350z threw two SES codes. P0303, P0300
 

My dad has a '04 350z with about 180k miles on it (he bought it new and put all those miles on himself).

We both investigated the errors a bit ourselves but it was late so on the next day he decided to check his air filters and they were super dirty. After cleaning the air filters he hasn't had the issue pop up again (its only been a few days though).

Do you guys think that was probably it or potentially something worse?

cylinder 3 was misfiring. that the middle plug on the passenger side.

have you changed spark plugs in that 180k miles?