Dave, funny you should ask.... Here's what I have found with the 103" motor and Harler Twin Cam's in general.
The 103" uses cast pistons and rings stock. The ring are thinner than the 95" motor's due to the thinner piston to accomodate the 103's stroke of 4.3. Thinner rings equals a greater chance of leakage, blowby, etc.
Harley cylinder's are notoriously out of round from the factory. I have recently changed pistons in my SEEG and the cylinders were .0025 out in varous locations throughout the bore. The service wear limit listed by Harley is .0020!!!!
Combine these things with increased cylinder pressure from more fuel and air in the chamber due to better cams and if a particular cylinder is on the edge you get oil in the chamber. Your situation with oil fouled plugs, oil in the throttle bore and deposits in the exhaust are all tell-tale. Additionally, poor breathing can contribute to this situation and, of course, the oil in your throttle bore could certainly come from running the breather hoses to the air cleaner.
I have seen situations where oil actually leaks from the exhaust ports due to the aforementioned piston/ring situation. If your predicament clears up by running the breather hoses outside then there's nothing to worry about...If it doesn't, these are some other questions to ask.
I run a breather crossover (old style Screamin Eagle) from the breather bosses in the heads and a long piece of Earl's #6 braided hose all the way down between the motor tranny and attach to the frame. it looks OK and gets the blowby away from almost everything. GOOD LUCK!!!!! [smiley=cool3.gif]