[GunMetalGrey]

Originally Posted by Rodan

Dealer is waiting for the part to complete the TSB, but no codes were set by the surging so they're clueless.

This is what I was afraid of... without codes or being able to duplicate the problem the dealer is essentially refusing to do anything.

I'm looking into getting the car on a dyno in Phoenix with a good GM performance shop to see if we can duplicate the problem. Other than that, I'm not sure what to do.

Anyone have a contact at GM customer service that isn't clueless about these cars?

You don't have any long hard corners you can replicate this on?
I had to take this approach until my car started throwing codes, but it only started throwing codes because I got the car to act up a lot more by repeating what caused it over and over again, also the less fuel it had in the tank the more it started to throw codes.
When I was down to 1/8 tank it got so severe I thought I wrecked my car at one point, it basically went into some sort of limp mode and slowly died on the side of the road. That created a check engine light. The car finally restarted and I drove it straight to the dealership.