Not current on the 105 but iirc:-
1 Static discharge wicks.
2 Disrupts turbulence that would otherwise hit the tail in certain descent/speed combinations.
3 The 250 engine real exhausts are 2 x "small" ones per engine; the "big" ones are shrouds to get the hot gas up and over the airframe.
Would be interested to know why the aircraft had to go and meet the
PR machine rather than the other way round.