As-is:
       Rate pack join
pack 80.0/s   -- -15%
join 93.7/s  17%   --

Always 1000:
       Rate pack join
pack 46.0/s   --  -8%
join 50.0/s   9%   --

x $i rather than x 1000 or x rand(1000):
       Rate pack join
pack 74.0/s   -- -14%
join 86.0/s  16%   --