The following runs nearly instantaneously:

(progn
  (cl-loop for i in (number-sequence 0 130000)
     collect (cons (number-to-string i) i))
  :done)


This seems to take a long time (didn't wait for it to finish):

(progn
  (cl-loop for i in (number-sequence 0 130000)
     collect (cons (number-to-string i) i) into pairs)
  :done)


Is this a known issue? I couldn't find anything in the bug tracker about it.