2008 Toyota Highlander Sport 4dr SUV AWD (3.5L 6cyl 5A)
All V6 2008 and newer highlanders will develop piston slap according to the dealer and factory rep I talked to. It causes the engine to sound like a diesel for the first 10minutes of driving. The dealership could not fix the issue and bought our vehicle back.
I'm writing this to help educate people about this and hopefully save someone from making the same mistake I did, purchasing a certified highlander....
Tighten up piston/cylinder wall clearance tolerances so pistons don't "slap" when they are cold.