Intertextuality or plagarism?

Intertextuality is the shaping of a text by using another text or texts. This kind of sounds like plagiarism to me, it sounds like you are taking another person work and making it your own. But on the other hand I guess that there are only so many ideas out there, and you can take an idea and almost make it your own. For example, in Pulp Fiction Quinton Tarantino takes things from movies that he has viewed in the past and he puts them in the movie. I will give it to Tarantino he takes those things he has learned from other movies and he places them perfectly in the movie. For example, when Bruce Willis' character is trying to pick out a weapon he looks at weapons that influenced Tarantino in the past. Tarantino is not the only one to use intertextuality, if you look at the New Testament there are references to the Old Testament throughout it. Intertextuality is everywhere we look.