2007 P71 crown Victoria. Extremely bad misfire.

I have a 2007 P71 crown Vic with 139,000 miles on
the body and 83,000 miles on the engine. I
swapped the engine from my 08 grand marquis.
After the engine swap the car ran great for a little
while with no problems. One day it started running
really really bad. Can barely keep it running by
holding the throttle 3/4 of the way down. It is
smoking really really bad and the smoke has an
overpowering gasoline smell. I unplugged the MAF
sensor but it made no difference. All the coils were
checked and the plugs were replaced with no
improvement. While running the engine and testing
the coils, it started making this weird sound that I
can only explain as sounding like a playing card in
bicycle spokes. I can't tell where the sound is
coming from. I removed the valve covers and
inspected the timing chains and guides, the valve
springs, rockers and camshaft. Everything looks to
be in good condition. I have a basic code scanner
and when I checked for DTCs it has no codes at all.  
What am I missing? Could it be the 140,000 mile
o2 sensors making it run like this? What could that
strange noise be?