Years ago, my '89 4Runner had been 'meticulously maintained' by the Toy Doctor, including documented valve adjustments, according to the PO. I checked the valves right after purchase, and one was being held open, with low compression on that cylinder. I adjusted the valve (hugely) and the compression came back (whew!). But, I had a new thought on the 'professional mechanics' at that shop.
Colo Springs, CO