Question 45 fps with just one particle system with HDRP VR

Hi,
I am using VR HDRP with a nvidia 2070 and i just place a particle system from this free asset https://assetstore.unity.com/packages/vfx/particles/fire-explosions/procedural-fire-141496 and gives from 90 to 45fps instead 90fps in an oculus quest 2 with 90hz i have, with vsync as doesn't reach 90fps sometimes it drops to 45fps, it is bouncing from 90 to 45 and 45 to 90. This is normal or i am doing something wrong?

 

"normal" depends on several factors the drop to 45 is normal if GPU or CPU time becomes too high, in that case the system switches to half frame rate, while interpolating the missing frames.
now, what causes GPU or CPU time to go up is another story. Could be anything, like Post processing, or the particle system itself. Most parts of HDRP are not very optimized for stereo rendering as it seems. In general, HDRP works well in XR, but certain features not.