For those that keep getting a P0172 code this might be of some help.

I was getting this code constantly even after doing a full stage 0. I'd reset the cel and it would come back after a few miles of high boost driving.

I finally replaced the o-ring on the vacuum tree and also sealed up the ptc on the intake elbow with silicone. The grommet that holds the ptc was hard and shrunk a bit.

200 miles later and a lot of hard driving, no more cel and no more P0172 code.

The vacuum leak was almost not noticeable when comparing the vacuum at idle before and now. The vacuum gauge read a steady 21in.Hg before and just a hair over 21in.Hg. Spraying ether on vaccum tree and ptc didn't cause any change in rpm. That's how slight the leak under vacuum was.

P0172 is a code for rich running condition and it was caused not by a vaccum leak but by a pressure/boost leak. Air that was already metered was escaping under boost.

If you have a turbo and are getting a P0172, check every possible place that air can escape under pressure. Spraying starting fluid around the intake and vacuum lines is a good way to find most leaks but a small vaccum leak turns into a big pressure leak when boost comes up.

 

Nice!