The a/c on our 94 940 wagon blows fine when I am not accelerating, but when I depress the accelerator I loose air coming through the vents and when I let up it flows strong once again

Can be caused by a vacuum leak in the controls. A hand vacuum pump with a gage to test components and hoses for leaking and for engine vacuum

Water level perhaps. When you hit the accelerator the water volume increases. Check your water level and make sure that your thermostat is opening and closing properly. Water level I'm thinking

Sounds like you have trash/debris in the vents or your A/C evaporator is clogged with dirt.
Clean everything out and it should be okay. While doing that check for loose parts like flapper doors etc.
A vacuum cleaner with a flex rubber snouts helps.

The A/C may need to be recharged.

u have a loss of vacuum to the ac mode control switch, this switch applies vacuum to diff vacuum motors to move air to diff outlets, dash, floor, defrost etc. either the vacuum line or vacuum resivior at the engine is leaking or the mode control is leaking vacuum.

The vent is controlled by vacuum. Check the condition of the vacuum hose associated with the vent control. What is happening is when you decelerate, the intake manifold vacuum increases, and a diaphram is slightly pulled giving you air in the vent but very little. In normal condition the diaphram wont even pull. Solution is check for a vacuum leak in the vent control trace it coming from the intake manifold.

I don't suppose you have a vacuum gauge you could "T" into line after check valve somewhere to see if vacuum present while accelerating? How hard is it to pull controls out to see back of them, and locate vacuum feed line?

You need to open the vent, under the dash. Check the cable and moving action assembly. Make sure that it is all moving correctly. Some of the newer hvac systems in cars work off of vacume but most work with cables. Not big long cables, just small lever cables. also check your seals and make sure none of them are broken. I often find this is a bigger probel, the seal is cracked or broken or just came off and needs to be re glued in place. Don't be afraid to take the vent tubes apart as long as you can remember where they go.

you have a vaccum leak some where on the engine start the car up open the hood a listen you may be able to the leak it will make a hissing noise

there should be a vacuum line running by the drivrs side shock tower that might be unhook are cracked