Question on Boxster 02 Sensor + intermittant power loss

Hi can you help please?
Boxster S 2000 yr 67K miles
I had intermittent power reduction with the engine under load. It ticks over perfectly and revs OK at stand still. No engine check light and no codes thrown.
Replaced MAF sensor correct and genuine part caused permanent reduction of power under accelerating load. Changed back to original MAF, power came back but with original intermittent power loss problem.
Found an exhaust leak triangle gasket white powder in exhaust on left side indicating lean running brown powder on right side. After gaskets replaced then Engine Check light came on for the first time. Codes suggested O2 sensor and MAF, replaced O2 sensor, and no more engine check light but still intermittent loss of power under load???
Since O2 sensor was changed and when the intermittent fault is not present, the performance is better than ever. When fault occurs, which is much of the time, it feels like the engine is not getting enough fuel or air or to much???
All coil packs were changed 2 years ago at 45K miles
I'm thinking the MAS is also playing up but with the faulty 02 sensor the new replacement MAS could not perform properly and caused permanent power reduction. Or, vacuum leak
Any ideas please


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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Boxster Oxygen Sensor Replacement - 986 / 987

[Wayne 962]

It sounds like you tried to replace the mass airflow sensor, when there might've been a problem with the oxygen sensors. I'm not sure if you tried the new mass airflow sensor with your new oxygen sensors. I would probably try this first, and see if this fixes the intermittent problem. Other than that, you need to read the codes that the fuel injection system is outputting to you when there is a problem. These modern fuel injection systems are pretty good at telling you what is wrong with them. But you need to read the codes at the right time. Also, if there is a problem with one component of the system it may show up as a code indicating a fault with another component of the system. For example, if the engine is running very rich, then an oxygen sensor code may be may be tripped because the oxygen sensor will be detecting a rich running condition in the exhaust.

- Wayne