The purge control valve should be located behind the intake manifold. It's
a small cylinder about 1" in diameter and 1" long with a vacuum hose coming
off either end.
I'd recommend just replacing the valve. In many instances, disturbing the
valve to remove it and check to see if it's open disturbs it enough that it
unsticks. An open purge valve is pretty much the only way that fueling can
affect how the vehicle runs.
If you do want to check the purge valve, see if you can blow through it
with the engine off. If you can, it's defective. Since the issue is
mechanical, a resistance check won't offer any useful information.