As with bicycles, it's a well-known fact that auto control cables stretch over time. This can cause the throttle plate to not respond as quickly or even open all the way, according to Autoblog.

A properly rigged cable system is key to a smooth, responsive operation and can be a tricky maintenance task for the average owner. Aside from a hefty investment in tools, you need to understand the system and how it functions to perform the task correctly.
There are many different types of cable rigging systems, but there are some general guidelines to follow in order to get the best performance out of your control system.

Getting Started
The most obvious step is to locate the correct control cable. This can be done by either looking for a label on the underside of the control box or by reading the owner’s manual.
Choosing the right cable is important because it will affect the control signal from the control box to the engine. The cable should be thick enough to reach the shuttle lever in both the forward and reverse positions without bending it or slapping it on the dash, but thin enough to prevent tangling with the engine controls.
Test the Machine
To test the cable, have your helper pull the throttle lever all the way to wide open. This is called WOT for short. The oh so fancy looking braided cable at the bail lever should deflect by no more than about 1/4 inch.