I would like to know what mileage you started having timing chain problems.
I am sure you have gone back, but they must be able to fix it properly. I would speak to the manager.I just had to do mine - changed at 157,000 km - the CEL was on and off for about the previous 5,000 km. My usual mechanic did not want to do the job so it went to the local GM Dealer. Timing works fine (no CEL), but there is now a serious vibration in the A/C compressor. Dealer claims that moving the A/C unit when changing the chains could not have caused the vibration. Apparently it is just a "coincidence" that there was no vibration when it went in and big vibration when it was returned. As you might imagine, I am not a happy camper!
Which GM dealer is that. Did you call GM directly to voice your problem with that dealership.did that - no success - they are happy to fix it, but at my cost - I don't think I want anything to do with them anymore - Until the G8 I had not purchased GM for years and now I remember why!