Might try testing the Throttle Position Sensor and Air Flow Meter for dead spots in their variable resistance regions:
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml
http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

A dead spot there can cause the sensor to give erroneous data to the ECU and that can cause symptoms like you describe.