Engine Performance problem
1996 Mazda 323 4 cyl Front Wheel Drive Manual 125000 miles

I have a 1996 Mazda 323 thsat i have had for about 2 years and now im having problems with the engine.
When i ´m driving and go from 1st to 2nd gear and so on the car wants to stall and sometimes turns off only when i put it in 1st again will it regain power...Ive changed the airfilter and gas filter recently but it didnt seem to stop the problem. It seems that the car is just loosing power.

Thank you