Block Lag / Buggy

When i play minecraft, I can get around 60-200 FPS but when i play on any of the new snapshots it brings my fps down to 30-40. Theres also block lag and somtimes chunks will just unload. After 14w30b Snapshot it fixed my FPS problem but the block lag and unloading chunks are still there. I hope they fix this befor the release.