with all the issues people are having with the 450's i wonder if an fpr would help startup/idle/part throttle? perhaps bumping it up to around 42psi or so would allow shorter pulses?

 

Well on a cold start-up that wouldn't help because your ecu is runing under pre-programed settings until it's warmed up. As far as part throttle that would indicate that it needs to be tuned better on a dyno, and idle, would also be v-afc setting that would effect that. Otherwise you would have to run extreemly low fuel pressure to adversly effect the amount of fuel entering the engine during idle.