self tuning 03 GTS with greddy supercharger

So to start off i have a 03 GTS with a greddy bolt on supercharger kit. This was my first car that was ever boosted and i got it with the supercharger already on it. Problem i'm having is that after driving for a little while when i come to a stop the rpms will drop below 1k and usually bounce up and down between 800-600 until eventually after a few more stops it dies although it will start up if you give it a few second after it does this. Also its constantly spitting out carbon out of the back and is running really rich after starting it up for a few minutes anytime I stop just a strong smell of gasoline. So with all that said I took it to a mechanic and he said its probably the tune witch makes sense to me. Problem is I don't know who tuned it last or how they tuned it so he told me once it gets re-tuned he will be able to tell me more of what could be other problems.

Now understanding all that and where i'm coming from here I want to try and self tune the car at least to get it to not die when i stop after 15 mins of driving. I've searched in my area and i cant find any place that does dyno tuning that's not like 6+ hours away and I don't make that much money. I have another car (its a mustang i got for $800 off CL so no I don't have money still) so this is becoming more of my project car. What would be a good tuning software to use and also some helpful resources like books or videos to help give me a better idea. I understand the basic concept of tuning a car but I'm certainly not experienced so any help would be great.