I have a 1996 Cougar, and have a new 22,000 miles Ford warranty engine in a car with 72,000 miles on the odometer. I have a persistant ping on acceleration or under any modest load (like driving up a decent grade). A year ago I replaced the air flow sensor, and this ping went away (but has returned). After replacing the air flow sensor a year ago, the engine really perked up, too.

Same thing happened with a 1994 I owned, too. Ping until we replaced the air flow sensor, then went away. Don't know if it's come back on that one as I no longer own the car.

Do I have to replace this every year or so to eliminate the ping and keep it running right? Is there any sort of other mainatinance (I have tried premium gas, but it doesn't help much) like O2 sensors, etc. The plug wires are new and as I said the engine only has 22K on it (I use synthetic engine oil, too.)

There is no need to replace the MAF sensor unless it is totally inoperative. Usually it just gets dirty, and the single biggest cause is the K&N air filters some people insist on using.

Here is a link on "how to" clean a MAF : http://www.crownvic.net/tech/cleanmaf.html

Thanks.

And, yes, I do have a K & N filter. Guess I should replace it with a standard paper element filter, right?

Yes. The K&N is actually costing you power, and filtering quality, despite their claims to the contrary.