Not sure if this is what Michael meant by the detent cable. I got this short write-up and pictures a few years ago for checking the connection of the throttle cable underneath at the governor:
Idle:
Attachment 72253
Floored:
Attachment 72254
Crawl under the car and look at the governor.
The rotating arm connected to the wire is what you are looking at. In the first picture it's where it should be at idle (actually this one is not completely "relaxed"). In the one where you can see fingers, it's where it should be when the gas is floored.
If it's out of sync where it's rotated more at rest, it will tend to hold gears too long. This also restricts the throttle throw, so if this is really out of whack you are not getting full throttle either.
