i dont own my 90 taurus anymore but from what I remember the tv cable had one rounded bend from the throttle linkage to the trannie, should have no sharp bends, there was also pretty much no other parts in its way, easy to way to check it is grab a hold of the throttle linkage with the car off move it back and forth and make sure the cable moves smoothly if not get it fixed or replaced! not only will a bad cable cause the car to shift poorly but add stress to your trannie which costs more to replace then a taurus is worth.
also check the motor mounts, i had to replace at least 1 in my taurus, i had the same really hard downshifts which where caused by a combination of broken tv cable mount on the linkage side and a broken mount.