This weekend while installing my FPR, I found that some of my stock fuel lines had become brittle and weak. While trying to pull off the stock return line, the line started to come apart in my hand. Now, I have 69k on my car, but I don't consider that a lot. However, over time it appears the lines have become worn from the heat in the engine bay. Running 34-44 PSI and you probably won't have any problems. However, if you are running boost or NOS, and high fuel pressures, you may want to consider replacing your stock lines as a safety precaution, better safe than sorry, or left stranded somewhere with a blown engine and fuel lines.... Hope this helps someone...

Oh yeah, make sure you get high pressure fuel injection line... It cost a lot more than regular PVC lines, but it holds a lot more pressure...