My '99 A6 has been well taken care of for the last 99,000 miles by me! The 6,600 prior it was driven from Alaska to Washington State with a photo of a mail order bride in the ash tray.... men are lonely in Alaska! Anyhoo, the engine light came on recently and my friendly Audi dealer tells me it will cost $3,000 to clean the carbon deposits out of the secondary air intake system. One of the technicians suggested that I use a gas additive to try to clean out the system... the auto parts dealer suggested a Mass Air Flow Sensor Cleaner. I now possess a can of this spray but have no idea how to use it. Can any one describe where I should spray this stuff? It is my last resort before I have to try to pass emissions testing in October.... don't want to dump 3 grand into an 11 year old car. Any suggestions welcome!