I have been working on a 2001 Sport 2wd with what I can best describe as a Surging problem at about 1800 to 2800 RPM. I happens under moderate acceleration best felt when going up a grade. The engine is 10,000 miles off a fresh rebuild and has been running great until this point. At idle the engine runs smooth outside of the RPM listed there is no miss it has good acceleration. I have swapped the A/F sensor, MAF sensor and Throttle Body. Air cleaner spark plugs and wires are all new condition all quality parts. The 4runner was fine I left it for 4days upon my return I noticed the Surge. I find no rodent damage in the engine compartment or at the Evap system. Any Ideas would be helpful. I have been looking at previous threads and have nothing that will help me resolve the issue.