My 5.4 LTR 24 valve fairlane has developed a serious miss after braking heavily.
I found leaking o rings on number 5 injector so replaced o rings,
Number 7 injector sluggish so replaced it.

Still missing, so I checked coil packs, no spark at number 7, plugged it into number 6 and got spark...
Ran hot wires direct from leads at number 7 still no spark...
Put multi meter on leads, 13.8v on the constant and varying between 7 and 11 v on the pulse....

Confused why I still have no spark on 7 pls help

Sounds like it could be a damaged ignition driver in the PCM for #7. Interesting how heavy braking can cause this and also interesting that you also have a problem with #7 injector. Is there something wrong with the harness that reared it's when heavy braking perhaps? Check that #7 wires for both injector and ign are not melted and shorting partially or fully somewhere?

How long since the plugs were changed?