The Dog

Are the engine parts identical?
I heard something about a second oxygen sensor, and that that's the real difference between the 2 ecus. Does anyone know anything about that??? Do you know where to look for the second sensor?
A am thinking of installing an 8d0 907 557 p ecu to my 8d0 907 558 e ecu equipped car.

ex-quattro PETE

In the Euro versions, you can't just swap ECUs because they have to match the ignition key. I think the matching can be done though, with a use of a VAG tool and possibly some special ECU codes from the dealer. I think I've seen the instructions on www.ross-tech.com for this.

If I understood it correctly, you have a euro-spec car with the 558e ECU which has an immobilizer, and you want to put in a US-spec ecu (557p) which does not have an immobilizer. Not sure if this will require the recoding, possibly not.

And why would there be an oxygen sensor inside an ECU???

ModifiedA4

i would think the bigger difference is emissions related stuff.

ex-quattro PETE

meaning he'd fail the emissions test with a chipped ECU or a US-spec ECU?

The Dog

The oxygen sensor is not in ecu. I was told that the us cars have 2 oxygen sensors, one right after the turbo and one before the cat. I do not know how many sensors the Eu model has and that's me problem. I do not know if the parts are identical. If they are then the car will work...
As for the immobilizer, it is not a problem since i got immobilizer 2 and the only think needed is a vag-com and me old ecu. You only need the dealer when you have immobilizer 3 in witch case you will need a special serial to change the ecus.