Attached is the pump down curve for IP12 pumping against its closed O-ring gate valve.  I'll isolate IP4 tomorrow for a comparitive reference.  

Regarding previous logs mentioning "remote leaks" or possible "permeation" etc...  I have since decided that I must have overlooked the 1 1/2" pump port valve during previous leaks checking efforts.  I likely had excluded it as we had recieved the rebuilt ion pump under good vacuum etc... and the pump-side flange of this valve has not been undone.  However, if this flange is "gappy" (I'll check tomorrow), the later act of me bolting on the small turbo pump to this valve could have induced a leak.  Spraying helium around the suspect HV feedthroughs and 16.5" flange joints (which are underneath the 1 1/2 valve) might have been cross-talking to the newly induced leak on the pump port valve.  

Heck!  Tomorrow is maintenance day and I will have access to this!  I'll just leak check the 1 1/2" pump port valve tomorrow and be done with it!