FastField slows down performance

Please note that using the Add-On "FastField" can considerably slow down your websites performance and interrupt with caching.
I've used the Add-On with much enthusiasm at first until I noticed performance decreasing. Looked everywhere but could not find anything until FastField was disabled.
Replaced all calls and even when no calls to FastField are made, performance was down a lot.

Hope this is of any use to someone looking for a reason why their MODx website is slow