Does using a virtual environment influence the performance of a web app?
Nope, it doesnt infuence the performance. Basically all what it do is changing python path to the virtualenvs ones. So there shouldn`t be any difference with performance.
I have a django app up and running. I never encountered any performance problems, though the app is hosted on a shared hosting platform. 
The provider asked my recently to use python's virtualenv. Since then the performance has been really bad, though I can't detect the change in CPU usage or any other statistic. 
So my question is: does using a virtual environment influence the performance? If yes, how?