2000 Jeep Grand Cherokee

Ok I need help with a cylinder misfire. The engine
has a hundred thousand miles on it and has only
been in the vehicle for one year. It came from
Gearhead. The engine has never run hot and the
cylinder 3 and 4 misfire usually would be a cylinder
cracked head, bad seal, gasket excetera. This is
not that. The plugs have been changed coil pack
has been changed wires have been inspected
crankshaft position sensor has been inspected and
changed flexplate has been inspected and all of
the fuel injectors have been changed. Everyone's
diagnostic tools including the one from Chrysler
simply says cylinder 3 & 4 misfire. It only happens
when you let off the gas and start coming to a
stop. Once it reaches around a thousand RPMs it
begins to misfire. The engine light flashes and then
you can't proceed from the stoplight without re
cranking. Each time you cycle the key off and on it
clears the problem and you're able to take off and
leave. It runs fine until you decelerate again. Has
anyone ever had a problem similar to this.