When I had my 1994 LS 400:
Very poor airflow from the aircond/climate control system. Fan works OK, suspect blocked filter behind glove box (for those of you who don't know where it is, there are removal instructions and pics in the Owners Manual).
Remove filter, it looks pretty clean. Notice what looks like a twig poking down from ducting above where I've removed the filter. Put fingers into ducting and pull out twig........big mistake. Lots of crud falls out and into the, now unprotected, air con inlet.
It took me a LONG time to dismantle various bits a pieces and get rid of all the crud.
I shouldn't have been surprised at the crud, the car was, at least, 10 years old.
So, every year after that, I did the following:
Remove filter
Place cloth over air con inlet
Poke around in upper ducting with a bent wire to remove all crud.
Clean filter by blowing through with air line (don't hold the line too close or you'll blow a hole in the filter). Blow from both sides. Wear goggles because the dust goes everywhere.
Remove cloth and crud and, immediately, replace filter.
You'll be amazed how much the airflow is improved.