EVO 3 PROBLEM. CAR KEEPS GOING DEAD WHEN I SLOW DOWN !!

I don't think that's correct at all, blow off valves relieve air pressure not push air in

As an Evo 8 owner, I'm not familiar with the specifics of the Evo 3, but I'm pretty sure the stock engine is going to be using a recirculating diverter valve. Does your current valve vent to atmosphere? The engine is likely calibrated to measure the amount of air coming in through the air filter, and then calculates how much fuel to inject for proper combustion. If the previous owner changed the valve from a recirculating valve (air is dumped back into the intake tract, also known as a diverter valve) to a vent-to-atmosphere valve (the air is dumped to the engine bay, also known as a blow off valve), then the car won't meter fuel properly for the engine, and you can have stalling and other issues. Daniel is correct - a BOV only let's excess air OUT of your intake tract when the throttle closes, like when you let off the gas pedal to slow down or to shift gears.

if you have it vented to atmosphere you should try to have it recirculated,, its most likely the problem

Oops sorry got it the wrong way around. Wow ok umm i will check it out. Thank you guys :)