[Rally Sport]

Alright, i'm new to the forums and cars altogether but read my story here for a minute. I started driving my car this summer right before school ended, I had alot of problems with it but got them fixed, then my mom doesnt let me drive it anymore because I got tickets and I laid off my car for a couple of months, and before I stopped driving it I filled it up with a tank of gas, so my car is sitting there untouched until one day I goto the store to get something, when I come on the way back my car starts to chug along, like it was losing power so I decide to give it some gas and it was going good until it just died and I had to pull it over, so I take it back and it sat at my house some more, finally I get to start driving it again but my car doesnt start, so my mom knows this mechanic and he goes and gives my car a tune up and my car starts going again, but I notice that it keeps dying whenever im sitting at a red light, he even changed the gas distributer and said it needed to be moved or something, so after a while I give up on it after I took it off and placed it back on properly, I dont know what it could be, he tightened up the accelerator and it made it not die as much, but same problem as always. I need help badly, im new to cars and this is my first one, which I love to drive, more than the other cars, it's a V6 3.1 any help is appreciated.