IPsec tunnel with awful performance

Hello! I'm new to Fortigate so I might be doing something wrong.   I have two Offices connected via IPsec between 2 Fortigates (201F and 601E). The performance is really really bad. Not even 100mbps in a simetric 1Gbps fiber. I'm using 6.4.5 on both Fortigates.   -I tried enabling auto-negotiate. Nothing -I tried disabling HMAC and ASIC. Nothing. -I tried disabling NPU and CP, so the encryption is doing it via CPU. Still the same bad performance.   I don't know what else to try to be honest. Thank you so much!