Im playing on a modded minecraft server with distant horizons installed just on clientside and on v2.3.6 (for some reason it doesnt load lod's on multiplayer anymore) i didnt used to get any lag and realising that something is wrong i updated to v2.4.3-b and this version always stutters exactly after passing a chunk border. From my personal testing and some settings changes , i have noticed that the fps drops from 160-70 and even 30 after running trough more chunks in a fast manner.