Oh man that's not good... Something wrong with the EGR I'm telling. I never got that code until I took the EGR off to change knock sensor.
BTW, had anyone see this?! What are the side effects? Car will run rich/lean? Any harm? This might be the solution for the P0400 LOL
http://cgi.ebay.com/ebaymotors/ws/eBayISAP...63#ht_502wt_939