Old thread and I'm never on here, but a search yeilded numerous results of code 401 Insuffcient EGR flow, and no one knows (or posts) how to solve it, so here is my $.02.

It is the EGR ports!

EGR is likely 20% of the issue, 80% caused by blocked ports.

look here for one writeup, there's more if you google - http://www.preludepower.com/forums/s...d.php?t=253704