Ford Focus Mk2.5 1.6 TDCI 109-AC problem not blowing air evenly + proper way to drive it (DPF)?

Hello everyone,

I've decided to come in here after noticing that my car's got a problem.

Just about a week ago a mechanic serviced it, basically, changed the oil and the filters (oil, air, fuel, cabin/polen). Yesterday i took the car out for the first time since the service has been done to it and turned the AC on for the first time since that day aswell (i tend to not use it to not consume more fuel because of the prices/liter) and that's when the dissapointment struck me. Turns out that, now, 1 vent blows strongly (nr 1 on the image) and the following 3 (nr 2, 3 and 4 on the image) blow it softly. Before this mess, all 4 vents were blowing the air evenly, with the same great force, but now, 3 seem to be asphyxiated.

¿Have you ever had this happen to you? ¿What do you think went wrong? ¿How could i try and fix it (Like, should it try to unscrew the pedal and pull out the filter and put it back in or something like that)? (The cabin filter is MANN FP 2440)

I wrote an email to the mechanic telling him about this and asking if this could be a mistake made when changin the cabin filter (which is located in a terrible and awful and uncomfortable position right next to the acceleration pedal so i would understand if the filter got squashed in poorly or something) and his opinion about what could be the issue. Got not answer yet and if i dont get any, i'll go in person.

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As for the second part of the question ¿What is the 'correct' way to drive this car? By correct i mean the way in which the car lasts as long as possible with minimal wear and, especially without clogging the DPF (Diesel Particle Filter). ¿At what revolutions should i change gears? ¿When does the DPF do its regeneration process; at what revolutions and speeds? ¿How do i know it is doing it? ¿How long does it do it for? 

I've seen some video on youtube commenting that this car has to be revd 'hard' and driven at high rpm like 2.5k-3.5k which are kind of scary numbers for me to see because i think 'high rpm > high pressure > more chances something might explode or wear'.

The car has 200k kilometers.

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Thank you for your help in advance