is PEP8 simply a style guide, or does it actually help the interpreter make optimizations to run your code faster? I'm simply curious since I really like PEP8 and wanted to know of any other benefits other than more readable code.
There is a single item in PEP8 that clearly has potential performance consequences:

Code should be written in a way that does not disadvantage other implementations of Python (PyPy, Jython, IronPython, Cython, Psyco, and such).

That is, PEP8 recommends that code be written such that it performs well across a variety of Python implementations.  This is a bit hand-wavy, of course (do you have to try all the available implementations?).
Other than that, nothing in PEP8 stands out as likely to impact performance or anything measurable apart from the storage space required for the code itself (e.g. four-space indentation).
Does following the PEP8 guidelines make your code run faster than if you did not follow it?