Seeing Darwood's modulator http://homepage.mac.com/darwood/egrmodulator3.jpg (I don't know how to steal his pic :-\ Someone please insert his pic of the carboned modulator ) has me thinking that a bad modulator could be the reason the rest of the EGR system fails. The bottom port on the mod. is hooked up via a vacuum hose, to the EGR pipe from the exhaust. Hot exhaust gas is what pushes the diaphragm of the mod in. When the mod's diaphragm gets a leak in it, carbon can get into the vacuum system of the EGR system (not good :'( ) With carbon in the vacuum system, the VSV can/could get plugged or damage the diaphragm of the VSV. Or (like on mine) the VSV would work one time I test it. Then the next time I test it it fails. Carbon could be getting stuck in the port of the VSV, triggering a code. Then the carbon gets sucked though the VSV and all is fine but there is still a code in the computer. When you go to test the VSV it tests fine. I could be way off on this but think that carbon should not be in the vacuum part of the EGR system.