Rough idle after warm start, Winter only

OK, 2001 XJ, AW4, 4.0l, NP242... no engine mods. I am getting a rough idle when I start the jeep after it is warm, then a CEL with the P303 and P304 codes. This only happens in the winter. Everything sounds like the heat soak issue (especially since it is cylinders 3 & 4, but in the dead of summer after a very hot run it starts and runs just fine. Since I am in CA (LA Area), I suspect it has to do with the "winter gas" formulation. As if we have winter in the LA Basin. Are there any additives I can try that will stop this phenomena? Having to reset the codes 2 or 3 times a weekend is gettign to be a PITA.

I have suddenly, well 3 weeks ago and have been chasing it since, have the same issue. It is so bad now, that a short hop to the store and sit 10 min, it won't start...unless I pour water on the fuel rail, go figure THAT out!