The gains are only the top part (non sweet spot) of the rpm spectrum? This is where AMG at least gives you tangible measurable sweet spot gains.
As for the suspension I like the improvements- 20% is lot for spring and dampener rates along with better steering.
Its only money- Id pay it LOL
2014 Porsche 991 Turbo S Guards Red
2013 Mercedez Benz SL63 AMG Diamond White
2012 Audi R8 V-10 Ibis White
2012 Mercedes Benz C63 AMG Black Series Obsidian Black