They have no functions in common
Ti-Se-Ni-Fe ISTJ
Si-Te-Fi-Ne ISTP
In fact they have a perfect compliment for there role the ISTJ has a connection with the INTFP and the ISTP has a connection with the ESNTJ.
The ISTJ has the ISTP auxiliary wing as its mood and the ISTP has ISTJ auxiliary wing as its mood.
Conches Point:3 - ISTJ 3w2 , auxiliary wing Point:2 - 2w1 agenda , second wing Point:4 - 4w3 ENFP mood.
Conches Point:3 -ISTP 3w4 , auxiliary wing Point::4 - 4w5 agenda , second wing Point:2 - 2w3 ISFJ mood.
The INTFP is not recognised but it is one of the two missing types and the other missing type is the ESNTJ.
On the enneagram these to types can be found at the subsidiary Points for both the 3w2 and the 3w4. The subsidiary wings for the three's is Points five and one.
I myself define these to types as being part of a component I define as the principle of unification. I have not a complete model of there workings because the complexity is vast all types are interconnected and there are many components operations between all nine points.
So it maybe easier to disregard my input but I shear it because the reader my have like me an awareness of these nuances and may kind comfort in knowing that another senses an awareness of these two types.
The So/Sx as an example draws upon the ESNTJ for its Instinctual capacities we can see this reasonably clearly within both the 9w1 So/Sx and the 5w4 So/Sx and the 4w5 So/Sx. if we have the savvy to observe and distinguish the subtleties and nuances of the sensitivities and sensibilities of these two types. Both types are components of the construct of both parts of the principle of unification.
I will not push the subject matter but I leave it for the reader to investigate.
