Flashforge Creator Pro - replacing plastic pulleys

My FFCP has has been a workhorse for the last year and printed more than 2200 hours without much problems, thats almost 8.5 kilometer of filament.

So yesterday i wanted to give my printer a good maintanance and took it apart, in the process i wanted to change the plastic pulleys. After putting it together again at first site this worked out great as i didn't had to change any of the original adapters, now when starting a new print the size of the printouts don't match anymore. After some investigation I noticed that the plastic pulleys are having 17 Teeths and the new pulleys i used are having 20 which might be the issue. Today i ordered pulleys with 16T to see if this resolves the issue.

I also started a topic in the flashforge group for this => http://www.thingiverse.com/groups/flashforge/topic:9788

Update 14/12/2016;
Just received some additional information from the topic created in the discussion group and seems you definitly need 17 teeth pulleys otherwise printed obje