Rules, regulations and registration of parameters are not 100% transparent when it comes to the registration of vehicles from the same brand and production or model year.
In the Netherlands e.g., most authorities deal with the different Euro-classifications directly linked to the date of the first registration for road use within the borders of the Netherlands. Even thought if you read up on the emission-standard as defined by the EU. This may very well be the case in Spain as well. Which may complicate your case or even make it impossible to object to.
I would strongly recommend an legal advisor from Spain to study your case, in comparison with the way Spanish authorities handle the different Euro-standards.
You may point to this information online at the Wikipedia website:
https://en.wikipedia.org/wiki/European_ ... _standards
The following diagram states the Euro1-5 definitions of the EU:

And if you scroll down on the mentioned page, you will find a table with the various requires exhaustgas parameter values for petrol cars.
If you check SAAB 9-5's currently for sale on the website Blocket.se in Sweden, and check their registered "Miljöklass"-parameters of models from 2000. You will find different information. 1st, did I not find a Euro-3 or Euro-4 label as such, but a description of the NOx output that was registered together with the socalled "Typgodkännandenr." which related to the document of the orginal declaration by the car manufacturer.
For example a SAAB 9-5 SE 4D 2.0T, which was manufactured Februari of 2000 and registered March 2000 is registered with a HC+NOx output of 0.2 mg/km according to the manufactures certified declaration with number e11*96/27*0073*07. Is has no registered Miljöklass but the Fordonskategori EU = M1 and the CO2 output is at 248 g/km
A SAAB 9-5 Aero 2.3T which was manufactured and registered Januari 2001 is registered with a HC+NOx output of 0.0 mg/km according to the manufactures certified declaration with number e11*96/27*0073*09. Miljöklass = MK1 Fordonskategori EU = M1 and the CO2 output is at 243 g/km (MK1 in Sweden relates to the quality standard of petrol since 1996, meaning that this is either a typo or something that is not been updated to a newer reference)
A SAAB 9-5 SportCombi 2.0T Automat which was manufactured and registered Januari 2001 is registered with a HC+NOx output of 0.0 mg/km according to the manufactures certified declaration with number e4*2001/116*0096*01. Miljöklass = 2005 Fordonskategori EU = M1 and the CO2 output is higher than the older ones at 251 g/km
The Swedish Transportation Authority declares currently since 2002 har nya miljöklasser införts: miljöklasserna 2000, 2005, 2008, EEV och El och Hybrid. So that gives an insight to the classification of the last mentioned SAAB from 2006 that is different form the older ones.
Because the Miljöklass (classification of the exhaustgasses) of a vehicle are defined by Transportstyrelsen after a notification from the car manufacturer in connection with the first registration and the class is based on the car model's exhaust gas approval, this does not cater for SAABs. Because the company does not exist anymore as a car manufacturer, no applications for existing cars can be made.
This is why you get no response from SAAB Hedin Parts. They are NOT the original manufacturer of your SAAB and can and will not apply for such a registration.
Another culprit may very well be that from the Euro3 standard the output of THC and NOx has been separated, but the Swedish authorities registered the combined value of these two in their registration database. Which may render the above information useless to your situation. But if the applications for SAABs back then are stored and legally accessible, you may have a chance there.
The only thing that you could do is debate the case with Spanish authorities based on the
European emission standards for passenger cars (Category M),[a] g/km, that your SAAB's exhaustgases as defined by the orginal documents that came with your car or another similar SAAB registered in Spain. Authorities tend to only appreciate documents that rate directly to your particular car that is registerd in your name though. So the latter may not be accepted as proof, unless you get hold of SAABs application at the Swedish Transportstyrelsen that may have these on file. I would recommend to apply for an certified copy of such documents.
This might in your case be e11*96/27*0073*07 But please check your manual or other original document and check the exact coding of the document. Otherwise your request/case may be disqualified.
Good luck, and let us know the outcome of your case. Since it may very well serve as a legal example for others.