P0134 and High emissions only at 2500rpm

[genetgenet]

Hi

I bought a subaru Outback Wagon with problems like the topic reads. It´s a 2.5l engine with a MAP sensor if it helps. At first i had a P0030 code and replaced the oxygen sensor and everything ran fine. A few days later i got a new code P0134. I had some leaks in the exhaust system that i fixed. I might still have a small leak before the sensors. Can this cause P0134? If so i don´t understand how that would work, it should still get reading right

 

Another problem is the when i was at the car inspection that the co level was at 3.3 (ppm?) should be 0.2. At idle it was 0.2. Is this related to the error code?