I have a 97 4runner 6cylinder, with a little over 300,000 miles. It has started having high rpm on acceleration or when going uphill. Will get up to 2,000 @ 30 mph, this is with me doing a slow acceleration-not "gunning" it! If I let up off the gas just a little (not even enough to lower my speed) the rpms fall back under 2,000, also making a low pitched noise- very hard to hear (almost sounds like the noise made by off-road tires on the interstate, but not nearly as loud, just a low rumbling) work done in the past 7 months- oil seals changed, new water pump, new spark plugs and wires & new tires all the way around.