‘Dead spot’ at WOT from 4500-6200 RPM

[Stroked & Blown]

Recently I have been experiencing a lack of power at WOT from 4500-6200 RPM.
It feels like the Variocam is kicking in 1700 rpm later than it should.

Based on the codes I suspect this is a vacuum leak, but wanted to check with the wisdom on this forum.

Codes:
P1124 oxygen sensing adaptation range 1 (cyls. 1-3) at enrichment limit
P1126 oxygen sensing adaptation range 1 (cyls. 4-6) at enrichment limit
P1128 Oxygen Sensing Adaptation Area 2 (cyls. 1-3) - Rich Threshold
P1130 Oxygen Sensing Adaptation Area 2 (cyls. 4-6) - Rich Threshold

Camshaft deviation is 0 for bank 1 and -3 for bank 2
1998 Boxster 5 speed/2.5L
56k miles
Car has test pipes (track)

Should I go chase down a vacuum leak or start elsewhere?

[Danimal]

When my MAF sensor started acting up it felt like power dipped around 4500-5000 and then surged after that. That could be another place to start.

[Stroked & Blown]

Thank you - removed the maf and cleaned it with some CRC MAF cleaner. Problem solved.