From Club3G: After the install the engine would not idle properly, but ran normal at higher RPM’s. I picked up a hand vacuum gauge and discovered there was a slight vacuum (3Hg) at the EGR valve on idle (should be none). This was opening the EGR valve at idle and causing the rough idle. If I disconnected the EGR hose, the engine ran normal. I tested all the valves and lines, everything was ok. Then I pulled the throttle body and found the problem. The VRX plenum will bolt up to your stock throttle body just fine. However, the throat is much larger. The stock TB has some vacuum passage ways that need to be sealed. The VRX plenum did not cover the gasket enough to make the proper seal. Here is what I did to fix. I found a machine shop with a band saw and cut the ½” lip off my original intake manifold opening. I used this as a spacer. Drilled the holes out and cleaned it up. This bolted between the TB and intake manifold (using two gaskets). It sealed the passage ways and bolted up just fine (needed to buy longer TB bolts). Vacuum fixed and EGR is working normally.
http://i1098.photobucket.com/albums/...muhylno/TB.jpg