2012 Dodge Grand Caravan - Code P0301

A couple weeks ago, the MIL light came on in
my 2012 Dodge Grand Caravan (3.6L).  When
I hooked up the scanner to read the code, it
said P0301 (Misfire in Cylinder 1).  It has just
about 92K miles on it so I figured it was time
for some new plugs.  

I put the new plugs in (verifying gaps on each
plug) and then I swapped the cylinder 1
ignition coil with cylinder 3 just to make sure
the coil didn’t go bad.  After I was done, I
took it out and went through the full drive
cycle.   No check engine light. I thought it
was good to go. About a week later, the light
came back on.  I figured it might have been
the #3 coil (old #1 coil), but when I read the
code it was still P0301.  

The van seems to run fine.  It doesn’t idle
hard and there are no other codes indicating
it is running too lean.  If it is still misfiring, I
read it might be a bad/clogged fuel injector
but why would it take a week for the OBD to
detect it and illuminate the CIL again?  Aside
from that, wouldn’t it idle/run rough?  

Where do I go next - Fuel Injector? PCV
Valve?  The Fuel Make-up Air Hose (aka
breather hose; or hose that goes from intake
to air box), has some oil in it in the part that
connects to engine, could that be related???

I’d definitely appreciate some advice.  

Thanks.