we're always tinkering with our bikes, no? what are the best changes you made to your rides that have improved both your race or training performances? i'll go first:
1) a pair of Dugast Typhoons in 32c. maybe it's just placebo but this rubber is so far better than any other tubulars that i've tried (Vittoria Cross Evo XGs, Challenge Grifos) it's not funny. So much so they should actually be illegal.
2) 1cm shorter stem. before the road bike and the cx bike were set up identically for position. but now with the shorter stem it makes a huge difference. no joke what an improvement it has made in being able to stay upright and move the center of gravity back over the rear wheel.