I have a pathfinding behavior set up yet it seems to work slow when there's a large amount of tile present in the scene.
The larger and more complex the graph is, the longer a search will take. Unfortunately, there's no getting around that--but there ought to be ways to optimize either your code or mine.
Make sure you don't search for a path unless it's absolutely necessary. If you're doing something like searching in an update event, try finding a way to reuse the previous result as much as possible. You might also be able to break down the map into smaller chunks, and search only within the chunk.
One way you can optimize the code in the extension is to modify the costEstimate function. See
this page in the documentation and
the reference it cites. In particular, note the "Speed or accuracy?" discussion. Keep in mind that I wrote a one-size-fits-all kind of extension that provides an "okay" solution to a wide variety of problems at the expense of not being a "great" solution to one particular problem. That website I linked was my main reference while writing the extension--so if you want to tweak it to better suit your purposes, reading through that post would be the best place to start.
Not knowing the details on what you're trying to accomplish, I'm afraid that's about as helpful as I can be.