DDoS Mitigation slowing site proxied through cloudflare

Hi, I recently bought a VPS with OVH everything was working fine, I just wanted to add cf to protect against l7 attacks, however when OVH mitigation gets turned on, for some reason it causes my site to have a significant degrade in performance, please note that this degrades only happens when I am accessing my site via its domain which is proxied through Cloudflare, I get no performance issues when accessing via direct IP.

At first I thought it might of been blocking cf ips, I have already added all the IPs to my network firewall rules (as from https://www.cloudflare.com/ips-v4), please advise if you have any idea on what to do.