Question on Boxster 02 Sensor

hi, i have an 02 boxster 2.7 egas, there is an intermittent idle issue that seems to come and go, where the idle jumps up and down. there was a code for the MAF so i have replaced that, the AOS, all spark plugs,ran a smoke test, replaced the plastic tubing and seals for the spark plugs, changed the oil,replaced the air filter, new serpentine belt, cleaned the throttle body,reset the throttle body, checked proper voltage of the battery with the car on, and off so the alternator is fine as well, checked fuel pressure which is fine, and needless to say i am still experiencing this random idle issue. it seems to kind of cut out under throttle acceleration and idle surge when at a stop, but as stated before it occours randomly, and is not constant, no CEL is on and, basically all i can possibly think of is that it might be the o2 sensors bad but not throwing a code? any input would be awesome, this thing has become a nighmare of a headache, thanks!

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[Casey at Pelican Parts]

You will need to check the fuel trim values, see which way the RKAT, and FRA are trending. Once you know that you can see which way to go. I would bet though...this is just an educated guess based upon years of experience and the fact that you've covered all other bases, your vacuum reservoir is faulty. Access the vacuum reservoir, apply vacuum and it should hold the vacuum you apply INDEFINITELY. Any loss of vacuum means that component is faulty. These do not smoke when faulty which has always mystified me. I applaud your troubleshooting prowess keep up the good work!

- Casey