LNF tune won't keep boost DTC P2261

I tuned a 2007 Saturn Sky Redline for a friend. The car baselined 238rwhp/257rwtq. The boost was right at 14.5psi. The (attached) tuned combo made 286rwhp/334rwtq. Boost was in the 23psi range. The mixture during the dyno session was quite a bit leaner than commanded so the MAF was tweaked in the upper flow range. The car ran flawlessly on the street, pegging the boost gauge at 23psi. Later, the friend reported that the car was only putting out 11-13psi. They were also getting a P2261 code. Can somebody please check out the attached tune and see if I made any rookie mistakes? I would appreciate it if you could tell me if this is something tune related or if the car could be experiencing some kind of mechanical issue. Thanks!

Attachment 42668

#PIP4182: SES Light And/Or Engine Misfires On All Cylinders - Inspect Ground - keywords - compression controls damage detonation dtc gt knock low mil no P0300 P0301 P0302 P0303 P0304 P2261 ping plug power - (Jul 13, 2007)
Subject: SES Light and/or Engine Misfires on All Cylinders

Models: 2007-2008 Pontiac Solstice GXP
2007-2008 Saturn Sky Redline
2007-2008 Opel GT
built before May 23, 2007
with 2.0L Engine (VIN X - RPO LNF)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
On rare occasion, various engine performance issues, such as engine misfires, SES light, no power, and/or detonation may be experienced. This may be the result of a loose engine ground on the left front of the cylinder head. If the customer continues to drive the vehicle like this, the concern will get more severe, and engine/spark plug damage may occur. Upon inspection, DTCs P0300, P0301, P0302, P0303, P0304, and/or P2261 may be stored.