PO171 and PO174

[VentureRick]

I have a 2002 1500HD with a 6.0 with 133000 miles on it, a couple of days ago it started running really bad but no check engine light came on, I was able to drive it back home and hooked the scanner up and it through these 2 codes, I cleaned the MAS air flow sensor and replaced the air filter and it ran fine so I cleared the codes and drove it a few miles then it developed a slight hesitation off of idle, I have checked for vacuum leaks and have not found any, checked the fuel pressure and its only running 25 to 30 pounds with vacuum line unhooked at the regulator, I changed the regulator and it still reads the same, what should the fuel pressure be and is there a certain way your supposed to check it, thanks in advance,