I cleaned out the entire PCV system along with the idle air valve (save for removing the oil trap). This was in an atempt to clear the high idle after highway use issue (stuck open idle air valve...which really wasn't all that dirty). Upon start up the car runs at a slightly higher rpm than I like, but then settles down after 10-15 sec. during that time it fails the oil cap rattle test. Once the rpms have settled to normal idle, the cap stays snug. Any ideas? Other than that the car seems to run like a top...i got 25mpg cruising at 70mph from Pittsburgh to Philly and 22.3mpg on the return trip at 75-80mph....not too shabby if you ask me....given that she turned 360,000 miles on the trip.