/**
 * Called on both Client and Server when World#addBlockEvent is called. On the Server, this may perform additional
 * changes to the world, like pistons replacing the block with an extended base. On the client, the update may
 * involve replacing tile entities, playing sounds, or performing other visual actions to reflect the server side
 * changes.
 */
public boolean eventReceived(IBlockState state, World worldIn, BlockPos pos, int id, int param)
{
    EnumFacing enumfacing = (EnumFacing)state.getValue(FACING);

    // ...

    if (id == 0)
    {
        // ...
    }
    else if (id == 1)
    {
        // ...

        // Comment: Replaced this
        // worldIn.setBlockState(pos, Blocks.PISTON_EXTENSION.getDefaultState().withProperty(BlockPistonMoving.FACING, enumfacing).withProperty(BlockPistonMoving.TYPE, this.isSticky ? BlockPistonExtension.EnumPistonType.STICKY : BlockPistonExtension.EnumPistonType.DEFAULT), 3);
        worldIn.setBlockState(pos, Blocks.PISTON_EXTENSION.getDefaultState().withProperty(BlockPistonMoving.FACING, enumfacing).withProperty(BlockPistonMoving.TYPE, this.isSticky ? BlockPistonExtension.EnumPistonType.STICKY : BlockPistonExtension.EnumPistonType.DEFAULT), 2);
        worldIn.setTileEntity(pos, BlockPistonMoving.createTilePiston(this.getStateFromMeta(param), enumfacing, false, true));

        if (this.isSticky)
        {
            // ...

            if (!flag1 && iblockstate.getMaterial() != Material.AIR && canPush(iblockstate, worldIn, blockpos, enumfacing.getOpposite(), false) && (iblockstate.getMobilityFlag() == EnumPushReaction.NORMAL || block == Blocks.PISTON || block == Blocks.STICKY_PISTON))
            {
                this.doMove(worldIn, pos, enumfacing, false);
            }
            // Comment: Added this
            else {
                worldIn.setBlockToAir(pos.offset(enumfacing));
            }
        }
        else
        {
            worldIn.setBlockToAir(pos.offset(enumfacing));
        }

        worldIn.playSound((EntityPlayer)null, pos, SoundEvents.BLOCK_PISTON_CONTRACT, SoundCategory.BLOCKS, 0.5F, worldIn.rand.nextFloat() * 0.15F + 0.6F);
    }

    return true;
}

private boolean doMove(World worldIn, BlockPos pos, EnumFacing direction, boolean extending)
{
    if (!extending)
    {
        // Comment: Replaced this
        // worldIn.setBlockToAir(pos.offset(direction));
        worldIn.setBlockState(pos.offset(direction), Blocks.AIR.getDefaultState(), 2);
    }
    
    // ...
}