Forward to specific pool and remove URL's path

The issue here is we do not have enough detail on what you want to achieve. When you make a request using /ping, are you expecting all the subsequent requests to now come from pool2? If so you need to add persistence in addition to the iRule. Start with adding source address persistence and see if that resolves your issue.

Here is a logging iRule you can use to track what is going on. Paste the logs to gist.github.com and drop a link here.

when CLIENT_CONNECTED { 
  set cid [clock clicks]
  log local0. "\[$cid\] Client Connected XXXX"
}
when HTTP_REQUEST {
  set rid [clock clicks]
  log local0. "\[$rid\] HTTP Request for [HTTP::uri] XXXX"
}

From the command line your BIGIP then use the following commands to get your logs

tail -f /var/log/ltm | grep XXXX