The first two characters are likely the byte order mark, this is automatically handled by the CSV Parser Snap. I'd suggest you use the HTTP Client snap and set the output view type to binary, then forward the contents to a CSV Parser Snap directly. Alternatively, you can use a Mapper or Document to Binary to convert the output of REST Get to a binary and then send it to a CSV Parser Snap. Below are screenshots of the HTTP Client snap views tab (with the output set to Binary), a pipeline to compare doing this with REST Get vs. HTTP Client, and a screenshot of the Mapper converting the entity from the REST Get to the content of binary output data.
