1992 Mazda MX3 cokes and stopes

Ok so i have a 92 mazda mx-3. The car is in great physical condition but i can say the same about the motor. I have the 1.9l V6 and it has 276000km on it. The starter fuel pump spark plugs and distributor caps were all changed but i have this really annoying problem. I start the car , i start to drive its all fine however once the engine warms and the idle goes down to about .8 rpm (starts at 1.5 rpm) it will start to choke. I'll be driving going about 50km/h and the gas just stops going to the motor. It makes a how can i put it ... farting noise. and sometimes the gas will slow down to the point where the car will stop in the middle of the street. When im at a red light il put in in first gear and the rpm will start going all over the place ranging from almost 0 to 2 and i dont know why... ive used injector cleaners about 3 times already (putting supreme gas when doing so) and the problem still persists. Ive contemplated of getting the 2.5 V6 from japan but im not sure if i should just try to fix this ... the problem is i dont know how... Can anyone help or shoot some ideas????