Allow me - as often happens - to be picky.
Strictly speaking PassPass will NOT "leave traces".
A single file is hex edited and after use it can (and PassPass has a provision for this) be restored "as it was before".
The mere act of accessing a system, no matter if "normally" (i.e. providing the user credentials) or "working around it" through the use of Konboot, PassPass or *any* other technique WILL "leave traces".
Whether these traces will be noticeable by a "common user", only by an "advanced user" or only by a "very advanced user" is - among other things - more a matter of linguistics and classification than anything else.
It goes without saying that accessing someone else's system without authorization is a CRIME in most countries, so - if you are really going to do that - you will better have the "right" paperwork authorizing you to do that.
I would venture to say that the mere fact that you (or "your company") even THOUGHT of accessing a PC "without leaving traces" and that you thought about using Konboot to do that shows that besides lack of experience on the specific tool there is a TOTAL lack of experience on any kind of forensic procedure, which is preoccupying.
Given the possibility that the whole stuff is illegal I won't provide more technicalities on the matter, but consider (and please let "your company" know) the following:
1) traces of the access will be left that CAN be found at a later examination
2) IF the suspect is actually "guilty" of something, he/she will EASILY be able to claim that whatever evidence is found has been "planted" on the PC at the time of the unauthorized access and in *any* following legal proceeding VERY LIKELY he/she will succeed