1995 Subaru Legacy Finally replaced starter

Ok starts with a year ago starting replacing the alternator several times now. Finally went elsewhere and got a different brand no problems so far Knock on wood. Anyways every now and then car just wouldn't start then you keep trying and would. Then got to point where I thought starter hit it few times starts up. Well just had it replaced thinking that was causing the alternator problem. Well now when I took it out of the shop the damn car will not start and stay running without my foot on the gas. I go to stop at a stop sign or light dies. Have to put in neutral and then keep foot on gas. Well last night the engine light came back on. And the car (funny as sounds) for about 10 minutes ran with out my foot on the gas. And I was able to stop at lights and stay running thought ok just run whatever out. Well then we went to store came out tried to start not had to keep foot on gas. And all the time again now. And sometimes it will start and stay running without foot on the gas but once you drive will not stay running unless your foot is on the gas. I was wondering if they put hte wrong part in my car? They have on my invoice imprenza and I have the legacy and just seems weird I get car has some issues but not like this. I've changed the alternator in past and had similar problem for a couple days car not want to run w/out foot on gas then it is fine in two days it's been a week now. Please help I just am not at a point in time where I can keep going to shops and having work done. And this makes me angry I could of done this myself and if this would of happen fine my fault this is nut.