I'm the original owner of this V79, with the base 5-cylendar engine. Has 83,000 miles. A year ago the engine was running rough and the check engine light was on. Dealer changed the #1 coil pack. Check engine light came back on while driving home. Dealer then found a sticking valve (I think) and did some major work mostly at their cost (believe this is a chronic issue with this engine). Less than 12 months later the check engine light came on again. This time the dealer said we first needed to upgrade the ECM (computer) at a cost of $235. We did this, and the check engine light came back on while driving home. Dealer now says we need a new catalytic converter at a cost of approx. $1,500. I've had the dealer do everything called for on this car at the appropriate time, used only fully synthetic, and am afraid that I'm entering a period where the maintenance costs are going to eat me alive. Thoughts? Is it reasonable for the catalytic converter to cost this much, and be going out so soon? THANKS.