I recently added a larger plenum to this setup, specifically, an H23A1 plenum that has beed reworked inside a bit (sharpening the port splitters, smoothing the transition around the throttle body) with accompaning throttle body. Using it allowed me to also eliminate the FICV and Cold Start Valve, and I performed a throttle body coolant bypass, and at last, no more hunting/surging idle. Compared to the stock plenum I might have lost a tad bit of idle torque with the H23A1 unit, but gained from about 2600 up. The lowend and throttle response is still better than the stock setup, only now I have a mugh stronger mid-high range. Peak gains are between 3000 and 4800, with no loss anywhere when compared to the stock intake manifold setup. I used my F22 TPS and have the idle srew turned out 1.5 turns. After driving for three weeks, I have noticed a 1.5-2 MPG increase on interstate, with slightly less gain in the city, as it turns out now I just pull out faster than before instead of being easier on the pedal!