[s-cars] 95 S6 "sputter"

[DGraber460 at aol.com]

My 95 S6 has just started exhibiting a "new" anomaly.
As I apply throttle (both partial) and full, he car will sputter (like if  
you put your tongue on the roof of your mouth) briefly and then pull  nicely.
I have not been able to check for boost levels and specific RPM, but  it 
hasn't been at only full boost or throttle positions.
Also it stored no codes, and has the contemporary coil pack  conversion.
Any ideas?
TIA 
 
Dennis
Denver