Alright, For every s/cer who has random misfire codes and has not a clue what set it off and why it goes off...heres my verdict.

I was driving back from work in pouring rain today; merging into the parkway i felt my car stumble and as i accelerated it got worse...once i got it up to speed it was alright. Then as i approach a hill on the parkway in 6th my car started to stumble again, which was when my MIL lamp came on again. I plugged in the scanner and i found 2 more codes then my usual P0301. Now i had a p0303..04..06. and the usual P1399.
The rain cleared up 5 miles down and my car was running fine again.

...THE ESM!!! As i mentioned before, its the CL guys who are being posed with the misfire codes. All the 04 ups rarely have any problems because they are provided a plug and play piggy back.

So what does the ESM do? its just a low budget signal modifier tricking the map sensor. Basically it sends a constant/perm. voltage to the ECM, when in fact its suppose to change according to barometric pressure (rain, mountains..etc)
Thats my guess...im not swearing by it..so don't hold it against me guys

i have my emanage and boomslang and will tune her asap and see how it goes from there.

 

good luck, wonder if it really is the esm?

 

I have the Emanage and boomslang and still get the misfire codes all the time so I doubt it's the ESM

 

are you running high boost?

it acutally happened again to me today; the manifold absolute pressure sensor HASS to be subjected to change in any situation to provide the proper info to the ECM; which predetermines the fuel delivery and timing....
so when it rains pressure is lower and the computer (sensor) cannot compensate because of the set ecm voltage.....
soo i dunno...
we'll see!@

 

Yeah, I'm running the high boost pulley as well