Hello, I have a 2005 CTS 3.6 which is running very rough due to the fuel injectors not firing properly. The issue was traced back to the ecm computer. I was told the replacement procedure would need to be performed by a gm dealer but was quoted $800 and $1000+ for a new ecm + install and reprogramming by the two dealerships I called which seems ridiculous for such a simple procedure. I see ecms can be bought used on ebay for less than $100 but how can I get them programmed to my vehicle without taking it to a dealer (they both refused to install/reprogram an ecm that I did not buy from them). I read that in another post that most sellers simply require your vin and can reprogram the ecm to your vehicle before shipping but have yet to find someone who says they will do this. Who can I buy an ecm from that will do this?