Truck: 2005 F150 4.6l
Mods: AF1 Cold Air Intake, Magnaflow exhaust

Issue: I've noticed lately that when starting the truck in the morning, as opposed to doing a normal high rev and slowly retreating back to a normal idle, it instantly runs at the normal idle speed... no high rev at all. If I run it and let it come up to temp, hop out and go into the store or whatever, then come back and restart, it does the normal high rev to normal idle.

Any ideas?

 

i'd clean the maf to start. also try priming the fuel pump first and then crank it, the check valve may be letting fuel leak back down into the tank.