Evidence of influence by Hitchcock?

I think there are many ways in which TESIS/Amenábar show the influence of Hitchcock,
but I don't think that Angela's thesis/dissertation is a MacGuffin.

A MacGuffin is merely a device to set the plot in motion and create suspense,
some sort of secret formula or contraption or conspiracy--the exact nature of it has no impact on the story, as you have noted.

The important thing is that everyone wants it or is afraid of it or whatever.

Well, Angela's dissertation is more meaningful than that. She is truly fascinated by her subject matter--violence--and it leads her to fall in love with a guy who is so totally wrong for her that she may not survive the relationship. She gets carried away with her research and it transforms her perception of reality. Angela and her thesis can be compared to Don Quijote and his chivalry novels.

But you find Hitchcock in other aspects of the film: the chase sequences, the paranoia surrounding sexuality, the theme of watching and being watched (like REAR WINDOW), the uncertainty over who is good and who is evil (like SUSPICION), the attraction to evil (SHADOW OF A DOUBT), etc.

As for PRIVATE IDAHO, this is a very iconic film for gay men. Amenábar is gay, so that could be part of the connection. It's been a long time since I've seen it; maybe someone else can find something more specific...

After further consideration . . .

. . . although the thesis/dissertation itself is not a MacGuffin (see above), the search for the camera equipment is definitely MacGuffinish. So I would say whatever that ultra-rare camera was that they had to find, that was leading them to the killer, acted as a MacGuffin in this movie, and so you were on the right track.

Email me your critique please if you get a chance.

When Chema pulled back the shower curtain I already had the Psycho soundtrack running in my mind.