'99 2.5L Runs fine, intermittent check engine light

[L1ttleBastard]

Hello,

My 99 2.5L Manual Boxster has just over 133K. Recently it's been the victim of a intermittent check engine light that will come on, go off, then stay a few days.

I was able to pull these codes
Porsche Error Codes6/8/18
P0410
Secondary air injection system Cylinder (1-3) Signal implausible

P1411
Secondary air injection system Cylinder (4-6) Signal implausible

P1124
Oxygen sensing range 1 Cylinder (1-3)

P1126
Oxygen sensing range 1 Cylinder (4-6)

P0442
Fuel tank ventilation minor leak below limit value

I cleared the codes with my Durametric and it's been fine ever since.

Any ideas?