Set the
Icon Animation to sync by
Particle Age and animate the icon when the first particles reach the bottleneck area of the tube.
Or if you have Max 2010 or higher, use a piece of geometry for the particles to slide on the surface of and a lock/bond test. Change it to
Lock to Surface, check
Restrict to Surface and set the position and rotation lock/bond % to 0.
3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC