Toyota Repair: Engine Pinging, combustion chamber, carbon deposits

Question
I have a Avalon year 2000 w/ 46K on the Odometer.
The engine is V6 3000 4 cam 24  VVT-i.
This car has suffered from engine pinging since approximately 15K.  I have had it into the dealer shop many times to fix and have paid  kmi many dollars but to no avail.  I have tried upping the octane with same(no) results.
Any suggestions?

              Thom G

Answer
First, get your money back or a credit. I hate it when people pay for repairs that didnt fix your complaint.

Try EFI combution chamber cleaner. have it done at a repair shop.
Read the owners manual. If it says regular fuel, than
DO NOT USE HIGH TEST if the car is designed to run on regular fuel. High test burns slower so you get incomplete combution that leads to carbon deposits in the combustion chamber.

May want to try a new fuel supplier.

Mike