So I noticed today with it being the first really cold day of the year for us my heater does not blow air out of the floor vents just the top vent by the window also when I set it to blow facing you as in such towards the driver it comes out of the vents very weak..
I feel like I can here air moving in my dash if I set it to blow directly in the driver any ideas where to look PS the dash has never been out of this car so not sure where to look.
Also does the 04 evo have a cabin filter I was also told to check the flapper door not sure where that is

 

These pages from the manual should get you started

First image is the cabin filter location (your EvO may not have had a filter but I think you can add one)

Second image is the beginnings to checking the heater controls. You may have a bent wire or a stripped gear

 

Ya I know how to get to those I fixed my heater control knob already but it seems like a flapper of some sort or something isn't opening down by your legs for the lower heat has me stumped

 

I never heard of anyone having problems with the blow-vent door on this car (not that you couldn't be the first). So, I suspect the cable.

The cable is supposed to be installed with the lever and knob in the defrost position. This would be where the cable is extended to the maximum and the lever turned in the same direction as far as it will go. Perhaps something has slipped.

So pray that is the problem. Otherwise, I think the heater box has to come out.

 

hate these issues,. prolly the cable

 

I just had this issue probably due to a lazy tech not fully assembling things after the recall airbag replacement.

Just put the driver seat as far back as you can and then get yourself or more limber helper to poke their head up under the dash board. Towards the center console you should see a cable for controlling the direction door for the vents. It is clear to see and isn't covered by anything. It is just a push on eyelet. So just push it back on and then turn your vent knob to be sure it won't just fall off again.