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Hi guys been trying to chase down this problem with my 325ci

Under hard acceleration cars rpm go up then there is a dip then away she goes, not so noticably in 2ns gear but higher gears more noticeably it is. For example if a hit the gas hard rpm will go to 3500 drop back dwn to 3000 before going back up this is all while still having foot down. Car is still quick though but i feel there may be power im missing! Lol

The cars done 140k miles, iv had the codes read and all that is showing is faulty o2 sensors

Any thoughts? Car was remapped before i got it and i wonder if its something to do with the tune?

Thanks chris
 

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Possibly DISA or if you have a ODB reader that can monitor the ignition timing see if for some reason the timing is being reduced a large amount.

Knock sensors should only cause the ignition to retard 3-5 degrees, maybe a bit more, but if you see the ignition drop back 10 or more degrees, then you need to figure out what may be causing it.

Also MAF may be questionable.

You might to try a MAF VE (Volumetric Efficiency) Test. Search the board here, but you will need to adjust for altitude and ambient temp to correct for the measurement.
 

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Forgot to mention a few things on the DISA.

Check the link in my signature below - Solve your misfires, lean codes, rough idle

I have an entire section on the DISA and how to check it.

Also there is a revised or newer DISA part number that is what you really should have. I believe there have even been cases of the DISA getting noisy and triggering the knock sensors causing the timing to be reduced, therefore reducing engine power.
 

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DIY job, very easy, just need a T40?? Torx driver. Check my link, there is a DIY video.

Part is about $200 USD, however, with VAT you may be up a bit. Not sure if you can get good pricing from the dealer or 3rd party like we can in the US.

Check for blown vacuum diaphragm and loose, noisy parts. It should be dead quiet when shaken hard, any rattle means it is self destructing.
 
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