post up pictures and i can help better.. but my guess is... being as the car is a mirage it is also a karman vortex mass air flow system. when you remove the "air box" and the pipe that heads to the intake the car has no way of registering how much air is entering the system there for it has no way of knowing how much fuel to provide, there for it runs like shit and dies quickly.

put the intake on properly and you shouldnt have any problems.