1999 Chrysler Cirrus acts like it is losing fuel pressure
 

I have a 1999 Cirrus with 137,000 miles and had the fuel pump, fuel filter, spark plug & wires, distributor, distributor cap & rotor replaced July & August 2013. Some days the car will turn over but not start, after a few try's it will finally start but run very rough and stall out. I have taken it back to the shop and they replaced the distributor and spark plug wires again. The car will run ok for a few days and then when it sits for a day it will start acting up again. Any ideas on what could be causing this? Thanks