Remove the plug and check for corrosion. A blue/green/white looking colour compound. If the pins looks clean check the signal voltage to the ecu at different RPM's. Can't remember what pin or colour it is now.
yeah check the AFM or your intake pipes that they are connected properly, took mine off to clean the Throttle bodies one day and ... didnt get them on exactly right (left one was rolled over)... and the Z was running like a V8/chugging to the servo (2 k away) to put fuel in when ir ealised what it was.