check your throttle position sensor (TPS) - once you determine which of the 3 wires (5v+, gnd, & data) is your data wire (by process of elimination using a voltmeter) turn the key on, but don't start the engine - slowly move the throttle all the way to the full open position, all the while watching the voltmeter. it works best with an older analog meter, but digital will work ok. if there are any points where the voltage suddenly spikes one way or the other (remember, we're only talking a max of 5+ volts measuring from gnd to the data wire) it needs to be replaced. if you aren't showing a nice smooth transition from around half a volt in the idle position, & near 5 volts in wide open throttle, it needs to be replaced. a tps can go bad & not throw a engine check code (had it happen more than once) and it will make it hard to keep running at idle. if that checks out ok, i would pull the air cleaner off & fire it up & watch your injectors - are they flushing too much fuel? if you disconnect the vacuum to the egr, does it run any different? if so, then the solenoid on it is stuck open - egr should never open at idle.