I posted a thread on a bucking problem a week ago and finially brought it to the dealer to have it diagnosed and found out that the converters were plugged and they wanted 651.00 just for the y pipe. The service rep also let me know that there is a federal madated warrany on these converters for 8 years or 80,000 miles. My truck had 82,000 miles and they said that they couldn't do anything for me. I also called GM directly and they gave me the runaround as well and told me the same thing. My advise, if you have a loss of power then get it diagnosed for a freebee converter. Got to love those gm engineers............