I was having the same issue with my 2000 SH with 112k miles (EGR flow insufficient). I read the posting for a EGR port cleaning DIY on PreludePower.com - http://www.preludepower.com/fo...75440
. I went to the dealership and bought the replacement plugs .30 ea. I wanted to do it myself, but was lazy since it has been very cold. I also considered using SeaFoam through the brake booster vacuum line to clean (hopefully) the ERG ports out. When I went to Advance Auto to buy an oil filter wrench, I saw Shell V-Power Fuel System Cleaner (a new product) and I bought a bottle. I poured it into the tank when I filled up with Shell SU2000, and after one and a half tanks of Shell SU2000 and mostly hwy driving, my CEL has gone away! I still might use GM top engine cleaner, SeaFoam, or do the EGR port cleaning, but for now I am going to hold off until the CEL comes on again.
Modified by TheJGB3 at 10:55 PM 4/2/2008