Finding JSON errors in .cfc

I am rendering a screen using AJAX / and a cfc. (No reloads)

All goes well until I make a boo boo and get a JSON error.

I know what causes it - text that should not be in the cfc. 

But now I've hit a brick wall.  I cannot find the "extra text" that's causing it.

Or ... is that the only cause?

The odd thing is the application runs fine on the bets server but not on localhost.

So I looked for any / all instances of "localhost" or 127.0.0.1 and nothing problematic.

Is there a tool out here that scans cfc's for these silly errors?

I have looked in the server admin logs but I have no idea which of the log files would house it.

Usually only use application.log

Thanks