Amplified world type lag

When I play a normal generated world there's a bit of frame rate issues (probably because of snapshots), but nothing major.

When I play in an Amplified world (even when no chunk updates are happening) the frame rate stops frequently for a couple of seconds at a time, and when I try to mine anything, I either have to break the block a couple of times until it actually breaks, or it just wont break.

Also the block breaking animation (the cracks on the block) flicker and show darker cracks than normally, and sometimes it doesn't even show up. These only happen on some blocks. Mostly happens in taiga, jungle, roofed forest and similiar type biomes.

This didn't happen before 1.8 snapshots.

• Sampsips