99 V6 problems. Need Help!!

[cyberstang5.0]

Try this...
Turn the key to ON but do not start the car... go to the rear of the car and your should hear a "whine" sound. That is the fuel pump. Make sure you hear that noise.

If you can, put a fuel pressure gauge on the motor. Simplest place is the shrader valve. Make sure she's getting 30-35 psi of fuel.

Next I would try to get the injectors cleaned. It has a lot of miles on it for it being only 4 years old.

Start with the easiest and cheapest things first, the work your way up. Also, trace the problem in the direction of flow (ex: fuel tank-> fuel pump-> fuel filter-> fuel pressure-> fuel rails-> injectors...)