Subaru Repair: 2000 Subaru Outback Pinging, subaru outback, subaru owners

Question
I have a 2000 Outback with auto transmission, 2.5 four cylinder engine and 81,000 miles.  I've replace the plugs, wires, fuel filter, air filter, front O2 sensor and had the fuel system professionally cleaned. I'm currently using premium fuel, but I still have engine pinging under almost any load. The shop told me that they checked the knock sensor and it was working properly.  They also said that some pinging is normal and that it isn't hurting the engine.  I like the car, but the pinging is very annoying. I've asked other Subaru owners if their car pings, and they've all said no, and they are using regular fuel. Is there some way to get this car to quit pinging?   Thank you.  

Answer
Hey I am sorry for the pinging noise.  First were the tune up parts dealer items?  I have learned over the years its best, sometimes crucial to use Subaru genuine parts.  A non NGK plug, will often cause a Subaru to run poorly.  The other possibility I can think of would be the timing.  A worn timing belt can slip causing the the belt to "jump time" or be out a tooth.  Also if the car has had a timing belt installed it is very easy to get the car out of time.  Even getting one cam out one tooth could cause the car to idle smoothly, and have slightly hindered performance. You can find out fairly easily, by removing the two cam gear covers on the front of the engine, and getting the crank on top dead center by the mark above the balancer.  The marks on the cams should be straight up and aligned with the two slits on the back side of the cam gear cover on the top of the cover.  If you don't see any marks on the cams rotate your crankshaft 360 degrees, and they should appear.  If you timing is out I would replace the timing belt, cam seals, crank seal, and possibility the water pump w/thermostat.  It is also a great time to replace the valve cover gaskets. I hope this is helpfull, let me know what happens!