I am just curious what is "normal" for throttle percentage readings. I have that gauge as an option on my Ultragauge. At idle I get 2% with full throttle only reaching about 94%. The WOT percentage readings take time to build up and traffic conditions never permitted full acceleration for more than maybe 5 to 7 seconds, but the percentage never got above 94%

Does all of that sound like my throttle cable is adjusted pretty much correctly?

 

My Torque app showed I was getting 95% throttle, I adjusted the cable and now it is at 99%.

IIRC, you can take the measurement with the key in the "run" position, but the engine doesn't have to be running.
Vector

 

I tried taking a reading with the key at "run" and the engine off, but my Ultragauge is a bluetooth device that sends readings to an app on my phone. Apparently it doesn't power up the bluetooth device unless the engine is running.

I was disappointed about that, but at least I can get readings while I am driving.

 

Ignition II may work for that.
On many cars (since about 1995), especially those with by-wire throttle, the car learns the min & max throttle positions all the time and treats those as 0 and 100% even though typically they're only near 0 and only near 100. Sorry to say I don't know when this was first added to the XJ.