Glad to see that someone may have already found a solution to this problem. I have a 2003 Silverado. I too am guilty of "topping-off". I'm getting both PO449 and PO455 codes. How do I ensure I'm getting the right part? I'd obviously like to get the $24 version since the dealer just told me it's $80 to scan it and then depending on the issue up to $500 to fix it. Please let me know if you need further information. The difference here is that you have a 2006 and I have a 2003. My GM part number is: 19152345. The AC Delco one you mention doesn't list this part number. I just need to figure out what the Suburban version of mine is. Thanks in advance, Brian
