well also the traction control being on. When the car feels that its not getting traction it controls the throttle response. Maybe you are feeling this problem. try turning it off and giving it full throttle this will change the tthrottle response. And a tune up will do the same spark plugs made a world of difference in my car

 

this is true, ive also heard of unhooking the battery and reseting the traction control ecu every now and then.