New air filter

My idle speed had decreased from about 500 RPM to 450 and the idle had become a little unsteady.

Ford recommended changing their original "super filter" air filter every 32,000 miles.
My impression was that the air filter was supposed to be changed every 24,000 miles.
Then I read on the internet that the air filter should be changed every 12,000 miles.
My air filter had about 16,500 miles on it.

I installed a new Purolator Classic Round Air Filter A30057 and my idle speed went back to 500 RPM and the idle became more steady.

Attachment 5889

The Purolator box says that "Replacing a clogged air filter with a new Purolator air filter can improve acceleration by up to 11%."

I cannot quantify it and it might be my imagination, but my car does feel a little bit more lively since adding the new air filter.

I will make it a point to change the air filter every 10,000 miles from now on.