Sounds like its too late, but for the archives, here's how to quickly and easily test your EGR valve and modulator.

1) Start engine and let idle for a few minutes.

2) Disconnect hose from EGR modulator to EGR valve. Rev up the engine (via an assistant or just moving the throttle lever). Make sure the hose from modulator to EGR valve has increasing vaccuum as RPMs increase. If yes, modulator is fine. If not, modulator is bad.

3) Hook the hose from step #2 up to the EGR valve. Apply vacuum to the hose (I did this by mouth, but a pump would be better). If the engine starts to sputter and die, EGR valve is fine (the EGR valve is opening when vacuum is applied as it should. Normally this happens at higher RPMS with advanced timing so the engine does not sputter. However, at idle, it will make the engine sputter). If the engine does not start to sputter and die, your EGR valve is probably stuck shut.

*Note: if you wanted to be real precise, you could test what the vacuum pressure is from the modulator as the RPMs increase and then see how much pressure is required to open the EGR valve. I think the valve opens around 2500-3000 RPM, so the modulator vaccum pressure at 2500 rpm should roughly match the pressure required to open the EGR valve.

Side note: I think my EGR valve is opening too early (rather than too late). I used some hardware (basically a bolt, a nut, and a few washers) so I can adjust the constriction of the vac hose from the EGR modulator to EGR valve. I'm still playing with this seeing how much constriction I can get away with before throwing a trouble code and how much of a gas mileage improvement I get. I'll post the results in a few months when I know for sure if it helps at all.

Good luck w/ your problem. Hopefully the new modulator will fix it.