Throttle cable not opening throttle valve completely?

On my 97 328is if I have someone press the accelerator to the floor, under the hood I can still manually rotate the throttle linkage another 20% before it stops. Is this normal?

Is the cable loose when the throttle is closed? If so, you can rotate the nut at the mounting bracket to remove the slack.

Yes, the cable has some play at the linkage. In fact, I can pull on the cable and a good 1/4 inch or so comes out.
How much tension should there be on the cable and do I need to adjust the foot pedal stopper or anything else too?

Thanks!

If you cannot feel any lack of torque or power, it is in normal position then, but you can always just take off the air inlet from the valve and check how much does it turn, when you put the pedal to the floor. If it doesn't open completely, you have to adjust the cable then. If it is like this, you should feel a little more better power when the pedal is kicked in the floor.

There should not be any pre-tension in the cable, otherwise you would have the trottle plate open without pressing the pedal. There should also not be any slack, so adjust that out for better pedal feel and throttle max opening.