Ok so my 97 4.0 5speed has ice cold air but couldn't blow out a lighter 6inches away from the vent. The middle 2 vents blow a little harder than the outside 2. I removed the glove box and can see the blower motor is working and isnt full of debris. However that is as far as I can get into the system. I was trying to get to the coils to clean them (they have to be clogged), but can't. Its seriously 110 degrees with the heat index so I have to get it working correctly.

 

Does air come out the Defrost vents better, this means you have a vacuum leak for the cabs vent system, usually in the engine bay

Is there ice forming on the AC lines in the engine bay fan box area?
That means AC is too cold, yes too cold and the evaporator is freezing up, so can't pass air thru it
It will freeze like that when it gets low on "freon", AC systems work by Compressing "freon" then letting it Expand in the evaporator to cool the air
If system gets low on "freon" it can Expand too much and too fast causing freezing, which is good for a freezer but bad if you want to pass air thru the frozen coils

You can also pull out the motor from engine bay side, just 3 or 4 screws, and put your hand inside housing, to the right, to see if there is any debris on the evaporator blocking air flow
Also check that the fan cage is on the motor's shaft tight, it can get loose so doesn't spin as fast as motor tries to turn it
Also after its reinstall, with key on/engine off make sure all the speeds work on the fan, you can HEAR the difference

There is nothing else between fan and vents/outlets, just the evaporator, no other doors that can block air flow, the doors just direct the air, they can't block it

One other thing
MAX AC pulls air from inside the cab, closes the fresh air vent
All other settings pull air from the fresh air opening under the cowl in front of windshield

 

DONT mess with the refrigerant charge until you first verify airflow. Do what RonD says. With the AC off (just regular room temp air) does the fan blow nice and strong? Ok good, so when you first activate the AC does it stay blowing strong for the first few minutes, but then gradually tapers off? If the answer is YES, then you have a refrigeration system issue.

BEFORE adding cans of refrigerant you need to have gauges on both the low and the high side ports. If you don't have these or don't feel like buying them, do yourself a favor and take it to someone who knows what they are doing. If you get your gauges on, I need you to report back what the pressures are when the system first starts, and when you start having these issues. Report back to me.
Low charge can freeze an evaporator. But so can a restriction in the system. The high side and low side gauges will tell me which it is. Adding freon to a system that has a restriction is only going to make matters worse, you haven't actually solved the problem and now all you've done is put a heavier load on your compressor.