Are there any vacuum lines on a 2005 Pontiac Grand Prix Base Sedan 4-Door 3.8L 3800CC 231Cu. In. V6 GAS OHV Naturally Aspirated? MY scan tool is showing a P0401 code (Insufficient EGR Flow).

WOW! You need to simplify and go back to basics. To answer your first question, yes, your car has vacuum lines and one is part of the EGR system. Start there and check/replace this line and the one from the PCV and see what effect it has.

I don't see any vacuum lines on my 2005 Pontiac Grand Prix. Everything is electronic. The car does not kick out a code when I drive it on the highway. It only happens when I'm going slower than 45 mph. I can drive several hundred miles on the highway with no P0401 code or any codes at all, but as soon as I slow down and run 35 mph or so for a while the code kicks in. I did have a bad PCV and replaced it. Cleaned up the air intake and all EGR passages, replaced the EGR valve, but I bought a cheaper one (so maybe it operating slightly out of specifications at slower speeds or rpm's). I did not replace the air intake manifold gasket. Could this be the problem or may it be a wiring problem that only occurs on rougher roads? It runs really good when the check engine light is not on and pretty good when it is.

I've had it to the dealership 3 times and they can't figure it out. LOL