Good troubleshooting plan on the above post; the upstream HEGOs are probably shot. Most likely the EGR valve is fine, but the EGR passages in the upper intake could very well be clogged, as the previous poster said. It may be a good idea to replace the DPFE module as well, because you'll have good access while the upper intake is off, and they're cheap. But when they go bad you usually get a P0402, or excessive flow. Still, not a bad idea at this time. Don't worry about your MAF right now, it's expensive and there's no indication it's bad. The IAC could be sticking, which can happen without setting a code, but again, save replacing that until you do all the first order items already mentioned. Don't forget to get replacement gaskets when you pull the upper intake.
