Much improved, thanks.
FSX SP2 flying PMDG 747X with ASX 1106. Picked a route that should have some shifts for tests. Departure and climb very smooth, some minor wind velocity fluctuations (2kts). At FL360 winds varied from 275/44 to 284/59 over several hours, all wind variations were smooth.
During descent winds/heading were not a problem with IAS fluctuated excessively. This I do not understand. At one point descending through 5000 the IAS was 170 with jumps to 190 that were very quick and about 2 sec apart; however, the wind was steady, pressure/altitude smooth, go figure.
I used FSUIPC settings to 1deg/kt change per 3 sec., no turbulence in either ASX or FSUIPC, ASX smoothing off, no enhanced route coverage.
Having reported this, I'd like to add that this was a major improvement to the violent shifts that I have experience before on many arrivals.
The IAS jumping around like that is really odd.