What are air tubes?

And I was going to ask you why you were still driving the car, but I guess that's a mute point. Probably could have saved you some heartache and a whole bunch of cash if you would have quit driving it.

 

+1 on air tubes? I had metal shavings too, but mine was due to the wall on a cam follower collapsing and the roller seized eating up the cam shaft.

 

I wasn't driving it for awhile. Once the rough idle started, I drove it 4 different times across 2.5 weeks trying to see if what I did fixed it. It is my daily driver, so had to use mom's vehicle in meantime

 

I had mice get into my air filter housing several times over the years...went so far as to put gutter guards on the inlets to my two mercurys- mice got into airboxes three times in 5 yrs, and twice in my mustang... they must love airboxes- luckily I had factory filters with the aluminum mesh, it kept them out of the motor. I always check now after storing more than a week before starting, just to be sure no wiring chewed/mice in filterbox, etc...

 

How did they determine the valves were bad? Removed the heads. With your first post sounded like you had a misfire from either spark plugs or COP. I would think anytime a repair is made to a rough running engine, a scanner should be used or the battery should be disconnected to clear the Keep Alive Memory which will reset the fuel tables the pcm tried to use to correct the problem.