okey now that im over that mass airflow problem, this came up. it all started after i replaced the stock muffler with a high flow after market one. and ever since my engine has been running on high idle much over 2000-2500 rpm. and even when the engine is warm already it still stay on 2500rpm on neutral when on a stop and the engine starts over heating. i checked my thermostat and it seemed to be functioning right. and checked the throttle body and even adjusted the idle screw by the throtle cable thingy. and still no difference. what else can i go check and try to fix or replace?

 

Check to make sure your tps is in adjustment and clicking when the throttle is first opened. To have an idle that high almost sounds like the cable or something is hanging up where where. It would have nothing to do with the muffler (BTW, the stock muffler is a high flow straight through muffler).