Odd, doesn't make sense especially on jb4 that m4 should pull on the stock m5 based what they run
https://burgertuning.com/products/s5...-g8x-bmw-m3-m4
if this is the same m4 with jb4 (might be more mods?), the gt500's usually run 6's 60-130, and we all know the stock m5 isn't running that stock.