Thanks for the replies
I ran a test using the 'convert float to string fast' from the ecosystem instead of the standard 'convert float to string' action included with playmaker.
Using the 'fast' ecosystem version had my game running at approx. 14fps
Using the standard playmaker action had my game running at approx. 30fps
I also see that unity gives many warnings that the 'fast' action is using legacy code that isn't supported anymore.
From my experience i suggest
do not use 'ConvertFloatToStringFast' action from the ecosystem.