p0172

Not sure where to put this thread but my girlfriend recently got an Fj because she couldn't afford a JK. lol, I know that's not the answer. I tried to convince her to get a TJ but she says they're too old. Anyway, the Fj forum is crap so I'm going to ask here. I'm getting 3 codes. A P0420...

I have a 2006 Jeep LJ with a 4.0 L6 running a Banks Turbo. I am having problems with a P0172 and P0175. From the long lists of common problems that could create the error, Is there a known single characteristic that causes this problem? Where should I start