Multiple Port wtih Pool Member and Virtual Server

In that case, I would recommend just creating 2 different virtual servers (one for each port: 80 & 8080). Then just use the corresponding pool for that virtual server (one pool using port 80 on backend and one pool for 8080). I think that would be the easiest thing for you.

The other option would be if the URL's are different, then you could use port 80 for both mobile and non-mobile and use an iRule to check the url and pick a pool based on that.