my car used to be an hf also, the egr valve is connected to the intake manifold close to the head on the left. it sticks up pretty high and has, if i remember correctly 3 or 4 wires comming out of the top of it. you might try removing it, its 2 bolts, and cleaning it out. sometimes the carbon in the exhaust can build up and clog the egr valve. (exhaust gas release). i would try that.