I noticed on my 2004.5 that when i lay into pedal while in park it accelerates fast and then takes a bit to slow down. i sthis the nature of the beast? nature of the common rail and ecm slowing down or what it kinda slows down in steps (jerky dropping)

 

If you rev it up really high in park/neutral....with a programmer or box, they will hang for a sec before they idle back down. Its normal....or at least my truck has done it with every box/programmer I've had....

No worries...

 

It's normal, even for stock.....it also does it in gear...

Go to an empty parking lot...roll at 5mph and blip (medium) the throttle and then let off....it'll do the same hang and not want to stop / slow for a second...

 

Give it some throttle while its cold and it'll drop quicker than it gets there...it hangs around when its warmed up though, even on my 6spd.