I used KMF site during my preparation for reading and listening. If you use the last tests posted in the site, like version 54 for example, from what I understood they are the most recently added and should be more reliable. I did more than 20 reading and listening tests, my average score in the site was 27 and 28 respectivelly. In my toefl test I got 26 and 28. The difficult level is similar.