I think I would start with changing the fuel filter. 2 years is a long time. This is a something you need to do regularly.
I would also check for vacuum leaks around where the upper intake meets the lower intake.
I would still get a fuel pressure test done, if these other things didn't fix it.
Let me know how it goes.
Thanks
Fordanswerman
FORD MOTOR COMPANY CAR AND POWERSTROKE SPECIALIST FOR OVER 16 YEARS. ASE MASTER SINCE 1991. CURRENTLY WORK AT A MAJOR FORD DEALERSHIP. GIVE ME YOUR FORD PRODUCT QUESTIONS, IF I HELPED, PLEASE HIT THE ACCEPT BUTTON. EXPERTS QUESTIONS ON FORDS WELCOMED