I've done a fairly tame stg1 tune on my 2.7 and was boosting around 16 psi...last week all of the sudden my boost won't go over 7-8 psi.  I did some logs and my specd boost through the whole rpm range was 1390-1410 mbar, actual boost was also around 1400 mbar(so i know it's not a leak).  Checked pedal position and I am getting 100%, so I logged specd load, which looked exactly like my LDRXN map, but specd load corrected stuck around 110 through the whole pull.

Now this morning getting on the freeway I noticed boost was back up around 15-16 psi for about 4 seconds then dropped back to 8 psi and would never go above it again.  I pulled codes, and get two:
Lamda sensor, Internal resistance too high - Intermittent
EGT sensor 2, Open or Short to Plus

Would either of those cause my problems, or does anyone have suggestions on where to start looking(still new to tuning)?

FYI - I am at 5000+ ft elevation if you're wondering why my boost gauge is off by a few psi compared to my logged mbar.

I had thought about that, but figured limp would be much worse so I dismissed it.  Guess I need to go get my hands dirty.

Thanks!