Check engine light is on for code P0174 bank 2?

My truck has many miles but has NEVER caused me problems. The check engine light came on but I assumed it was because it was close to 200,000 at the time. Now, in the last month, I have had to get it hooked up to a diagnostic machine 5 times and the check engine light gets "triggered" and comes back on. I have had the 02 sensors changed & its still showing p0171 & p0174. When it idles it starts to act like it is going to die and just barely stays cranked. I had another mechanic hook it up & he says that the 02 sensors are fine, so what are my other options to try & repair?

Use to set about 200 miles or so now less than 50. Idle sounds like a deisel rattling valves. Sets very fast if put under load. Found dry roted hose to brake booster replaced no codes 2 weeks later setting less than 50 miles. Cant find any vacuum leaks. Poor milage. Under load every now and then about 6 monthes it will set P0171.