uh... where? :confused:
what i did to mine was cut the whole top out, and widen the filter plate thingy. i did this by taking the filter off of the cage, putting the cage on the plastic plate, taking a marker and drawing a line around the INSIDE of the cage, and cutting out to the line. BUT, make sure you leave the little extensions for the wing nut, or you won't have a place to anchor your filter. you'll know what i'm talking about when you get it out.
then, you jet the bike right. since i live at 5,000 feet above sea level, the stock jetting was fine with a little fiddling with the FUEL screw (the tt-r has a fuel screw instead of an air screw, so it is opposite of what an air screw does, i.e. out=richer, in=leaner)
when the plate is cut out, about 3/8 inches all the way around, then you cut 1/4" off the filter base, all the way around, just to be safe. when you put the filter back in, (remember to clean and oil first!), make sure the plate goes in BOTH grooves, top and bottom, or the engine will suck dirt and virtually sand blast the piston and cylinder. :eek:
hope that helps,
-Rob