Your build date is written in the door jam, drivers side. I also have a 2006, unfortunately it was built in 11/05. I had all the symptoms in this thread and finally had it fixed. All good now at close to 190K.
As far as I can tell Toyota started using the "other" HGs around 12/05.
2006 (11/5 Man. date) SR5 4x4
Long time lurker
I was showing all the symptoms in this thread so I decided it was time to get it fixed at 175,000. I originally bought the 2006 having known about the HG issues with the older 4th Gens. Thought I was in the clear until a few months ago when I...