VSS is vehicle speed sensor. If it has needed a coil pack you have enough miles on it to need spark plug wires. They fail at their worst under a load. If you think it is an injector problem run some cleaner through a tank of gas. Make sure your battery terminals are clean and tight. Is it still under warranty? Don't think it would be an O2 sensor. When they fail they usually make the engine run too rich. You would be getting a CEL if the O2 sensor was bad. Sure sounds like an ignition problem. I had a Corvette that did exactly what you describe. It had water in the tank. Being heavier than gas it got in the pickup. I put some HEET in the tank to absorb the water and it ran good after that.