Stalling and misfiring

I just bought this vehicle used. It has an Inline 6. It is having problems with just cutting out and shutting off, especially when I'm accelerating or braking. When I come to a stop, most of the time it just straight up quits running. I think it might be the fuel injectors or the fuel pump, but I don't know, that car hasn't been driven in a while, the previous owner said he thought it was the ground wires, but he cleaned those up and it did it less, but it still did it. I just wanted to get your opinion on it. Also, it does it way more when I put the transmission in power mode, over comfort mode, and/or put it in 4x4 mode. Also, it starts to overheat in 4x4 mode. Sorry for the long text, but I really want to get your opinion on it before I take it into a mechanics shop and spend a bunch of money. Thanks