I have been racing a 1994 Mustang in BP/STO since the classes inception.
One area that has always confused me was the additions and subtractions for the rear suspension.

The GCR says:
"8. STO and STU cars that come with a solid rear axle or trailing
arm suspension are permitted an aftermarket or fabricated rear
suspension. Cars with an altered rear suspension must add 50
lbs. Cars with live axle rear wheel drive may reduce the minimum
weight by 50 lbs in STO and STU."

So my car has the factory live axle with an aftermarket EVM 3-link.
Do I get a 50 lb reduction in my base weight or is my aftermarket rear suspension considered and 'altered' rear suspension?
And if so, why the convoluted wording of the rule?
What qualities in a rear suspension must be changed for it to be 'altered'?