When updating my server world to 1.13 it acts as if it lags even showing > 60FPS.  Downloaded locally and ran single player to same issue.  Redstone lags 3 to 1 over 1.12. TNT and arrow usage also extremely lagged.  Also noticed same problem when trying Ilmango's cobblestone farm example world. I am unable to load my world as the limits prevent it.  I will upload Ilmangos 1.13 optimized cobble gen world as a reference.  My world is currently online as 1.12.2 at spacerite.serv.nu and is whitelisted so let me know if you need access.  The zip file is 212meg which makes it to large to upload here.