Any Idea what this is supposed to fix? I told them it was idling rough, and they said this fixes that. What else does it do? Will it improve performance?

 

They probably did this:

Subject: LSJ Fluctuating, Unstable or Incorrect Engine Idle
(Reprogram ECM) #06-06-04-039 - (08/10/2006)

Models: 2005-2006 Chevrolet Cobalt SS Supercharged
2004-2006 Saturn ION Redline
with Ecotec™ 2.0L I-4 Engine (VIN P -- RPO LSJ)
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Condition
Some customers may comment that the engine idle may fluctuate (idle roll) a hundred rpm for several seconds when the engine is started hot or cold. Further diagnostic investigation with a scan tool may not reveal the cause. No other driveability or performance concerns may be reported.

Cause
The most likely cause of this issue may be that the engine calibrations need to be updated to correct the fluctuating engine idle .

Correction
DO NOT replace the throttle body, the ECM or any other parts.

Reprogram the ECM with the latest calibration. This calibration, or any that follow, is designed to address this fluctuating engine idle concern. Refer to Service Programming System (SPS) in SI for reprogramming procedures. As always, make sure your Tech 2® is updated with the latest software version

 

my dealer is DUMB i ahve that excat problem with my cra and my delaer knows **** abot this pcm flash or anything thats going on....
they dont even have the door bezel trim fix yet!