Don't Be A Dick Inerdia
I never even knew GTKR had a working plugin system, so I can't tell you where to get plugins, but if you want to debug your map you might as well be best off debugging in the game.
Is this for Q3? Use r_showtris to see what the game renders and notice how the visible set changes as you move around. Learn how to use structural, detail and hint brushes in a good way by reading this:
(Finding that took me a good five minutes after PQ's wonderful restructuring.)
I Know How To Do That...
I know about detail brushes and hint brushes, etc., but the thing is that my map takes for ever to compile - slowly gobbling up memory, until it tries to take up more memory than my computer has, bringing it to its knees.
This is for W:ET.
Perhaps it is your light and shadow calculations. Is your lighting being put sparatically with large number radi?
Is your map inside a giant square to prevent leaks?