poor air flow in cabin on 1995 BMW 540i

My ac/heat seems to work okay and I can hear the fan running but the air flow is very poor. I think the cabin air filter needs replacing but it is not where I expected to find it based upon info I have read on the web (ie two filters on either side of the engine) Where might they be ??

Asked by for the 1995 BMW 540i
This is picture i created illustrating the locations and steps

It is very common for the fan speed resistor to fail and cause similar symptoms, the fan speed will be displayed on the indicator but the faulty resistor could be making the fan spin at half capacity. Possible
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THE E34 MOST common problem!!
Cabin filter clogged.
Remarkable improvement if you can put up with fitting a new one-that is why it has never been changed and will be completely blocked!!!