Is the check engine light on? Does it have any good acceleration in any gear? Does it stall or just act like it? Are you planning on doing the diagnosis and repairs yourself or do you just want advise for dealing with a shop/dealer?
I suggest you have the computer scanned or have a drive test performed with a scanner capable of reading the live sensor data. This will eliminate all or most of the guess work and save time and money.
If none of your sensors/ignition system is at fault, I'd move next to the fuel system, as those problems don't always show up on the computer.
Begin with pump pressure, filter, regulator then fuel injectors.