My '91 22re, 4wd pinged(light knocking, right?) always from when I aquired it at 142K miles here in So. California, and when the service guys swapped in a rebuilt long block at 164K miles, and bolted on all the old EFI and engine control peripherals, it knocked(sorry, pinged) EXACTLY the same as before. Flash forward 3 years to now...I put regular gas in it(which makes it ping like crazy) and take it to my local Toyota dealer. The sevice tech AND his boss take it for a test drive, come back and report: 'Oh, yeah, that's normal. Don't change a thing.' Same as yours, higher octane gas makes it less, retarding the spark advance makes it less. Interestingly, when I drove it to Utah, it stopped pinging with the first tank of Utah gas I put in it, and started pinging again when I started putting Arizona gas in it. Cal. gas = Az gas, more or less, I guess. I'm tired of trying to stop it from destoying itself. Cheers, Keith B.