You mean this one ??

>anyway, the purge valve...if I take the vacuum line (from the engine) off, the engine runs poorly. If I take it off and plug it, the engine runs fine. What is this information telling me? >

That only means you have taken a vac hose off and created a vac leak that has resullted in a lean mixture , resulting in a poorly running engine...and then you fixed the vac leak you created by plugging it and now the car no longer has that vac leak and that has corrected the fuel mixture and is running Ok again..that's all it means,,it has nothing to do with checking the Purge system , as that would be upstream for what you did.
You simply made a vac leak.
If the purge was not working, you would most likely see a purge code.
Check if you do. You would be looking for a 21 on DM or a 36 on HFM [pin#8]

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A Dalton