runnin a wet cyl isnt to good for your engine.

http://www.minibite.com/america/malone.htm

Hard to imagine how an insufficient EGR flow (if it's even real and not a
bad DPFE) might cause your #2 cylinder to be wet and misfire. More likely
it's a leaky injector or an ignition problem. And just in case: new engine
and all, but has your mechanic even checked compression on that cylinder?
In any case, I would recommend not to drive the van in this condition. The
unburned fuel may damage your catalytic converter, adding much more than
$270 to your cost of repairs.

IIRC, the 4.2 has ported EGR flow... each cylinder has it's own EGR passage.
There have been times when all but one or two EGR ports have carbonned up
leaving the engine with insufficient EGR flow but one or two cylinders WITH
excessive EGR flow... The resulting mixture dilution can leave enough
unburned fuel in the cylinder to wet the plug down.... EGR port concerns are
easy to test for - with the engine running, apply vacuum to the EGR
valve.... the engine should begin to run very rough or even stall....

Having said that, the DPFE sensor itself has been fairly troublesome...
These too can carbon up  making the PCM see low EGR flow when, in fact, flow
may be normal or even excessive as the PCM increases the duty cycle to the
EVRV to compensate...

In the latter case (especially if the EGR system passed the vacuum test), it
would be wise to consider looking at compression, possible injector concerns
or even ignition system concerns... and yes, waste spark systems can misfire
on one cylinder only...