The more I read through the forums, the more I think that I may need to change plugs/wires. A couple of tranny fluid drain/fill's probably would not hurt though. Perhaps I am mistaking "slip" for engine hesitation? My wife drove it on the freeway and came home telling me that the 4Runner was jerking as she was trying to accelerate to pass vehicles over 55mph. My 4Runner has 137,000 miles on her, and I bought her "Certified" at 47,000 miles. I have not been the most diligent about preventative maintenance.