Could you post a recording of you practicing that movement?
I just performed the Rach 2nd with orchestra a couple of weeks ago.
There are quite a few difficult passages, technical, musical and ensemble.
Obviously without hearing you, not much I can advise you on, however, a few points:
-beginning to rehearsal 3, make sure that the first bass note comes out, while still remembering that the orchestra has the lead in that passage
-8 measures after rehearsal 3, do not rush be steady. And let the orchestra do the accel leading to tempo 1
-make sure that your first melodic entrance is like singing. Romantic, rubato, but be careful, not too much
-17 after rehearsal 6, do not rush, be steady.
-make sure rehearsal 7 is as clear as possible
-rehearsal 9, the orchestra has the melody
-9 after rehearsal 9, I would keep it steady and wait till the Allegro to accelerate
-pay attention to the trumpet entrance at rehearsal 10
-at rehearsal 11, very romantic, sing it.
-23 after 13, make sure the eight notes come out.Not too much, but still clear and steady.
I hope the above helps you.
Obviously if I hear you,especially live, it would be easier to help you.
I am available on Skype if you are interested.