compression causes heat, which in turn does 2 things: 1. heats up the air which everyone knows colder air results in more power, and 2. the back section of the screws (where the air exits the blower) is the hottest and the screws themselves increase in size, and bang into each other resulting in metal shaving entering the engine
"Just how hot is hot? At crazy high boost 100-degree incoming air becomes 350-degree outlet air-that's a huge heat gain for a twin-screw blower. Jim says he horsebacks a 10-degree gain per pound of boost. Thus, when boost arcs into the 25-pound stratosphere, the hot blower rotors have expanded enough to crash into each other, destroying themselves and sending gritty metal bits downstream into the engine. The rotors always touch first at the gear end (discharge end) of the blower because it is considerably hotter than the inlet end, which you can think of as air-cooled."
-again from the same mustang magazine, http://www.mustang50magazine.com/tec...ger/index.html
the last part really isnt an issue unless your running high amounts of boost