To the OP, to answer your question with the most amount of details, take your time and read the following tread:
Gas Pedal Delay
Pay attention to the writings made by juld0zer towards the end of the tread. Here he (and other members) will explain (with important information) the reasons behind the "small delay" and the not so quick "throttle response".
I hope it helps you understanding the cause as it did for me.