I emailed Jetchip about the availability of any ECU upgrade for the 2003 Malibu (and I think it should work for any of the 3100 3.1L V6's, but I would check) and they responding saying that they do. Here is the reply:

"We do have a Power Control unit available for your application. The PCU box
would mount under the dash and you would route the wiring out under the
hood. You will have to tap into the TPS wire and splice the MAP or MAF wire,
depending on the application. The PCU will gain an average of 10-12 hp on
most applications. Suggested retail is $259.95. Contact customer support at
800-535-1161, from 8am to 5pm, M-F PST for specifics."

I ordered my transmission cooler from Jegs and it came today, along with a catalog, and they have what I think to be the model I need for $199 US. I'm going to call Jetchip to an exact model number and then compare it to Jeg's. I'll post an update when I find out.

If anyone has used this or any other Jetchip Power Control Unit (the kind you mount inside and is defeatable) please reply with your thoughts and results of installation and use. Thanks!