hey man i have a 99 wit 120k and i have pinging, i live in canada, i work part time @ walmart doin oilchanges, tires, all that **** ohh and ENGINE TREATMENTS, k i went for training the other day and they wanted to show us how to do an engine treatment, so i said yo can u do it on my car, so they did, they used slick50 engine treatment, u cant buy it in the store, they only do it in the shop, so basically it is 2 bottles, one goes in the tank on a 3/4 to full tank and they pour the other bottle into this little machine that connects to the hose thats connected to the PCV valve, basiccally that hose is a vacume, so as ur car is running the treatment slowly gets sucked into the hose and goes through ur whole gas flow after about 10 - 15 mins as the process is done, when i reved up my engine, all the **** that was in there had came out, black smoke flyin out the exhaust, honestly the pingin was gone complety, and it felt so clean when i was driving, the cost of this at walmart is $50 CAN, so in the states is about $30, honestly man go to a walmart and ask them to do the slick 50 engine gas treatment, if u do it let me know how u felt about it, later man