Hi again.
So it appears that port 60128 is the one being used by the iControlAV app.
The bad news: Those commands aren't standard Pioneer commands. They bear a strong resemblance to standard Pioneer commands, but are formatted very differently. For instance, the command "!1MVL82" resembles the standard volume change message "VOL082". The "ISCP$!1FLD..." commands resemble the standard "FL..." display data status update messages.
Since it's not using standard Pioneer commands, the plugin can't really be easily adapted to work with it. It'd be more than simply changing the telnet connection port. Plus, those commands aren't (yet) documented anywhere, so updating the extensive command list within the plugin would be a complete trial-and-error affair.
You might check to see if there's a firmware update for the 1131. I doubt an update would change the feature set, but you never know. If Indigo integration is important, you could use some kind of Indigo controlled IR blaster to send remote control commands to it. You could also do some packet sniffing between the iControlAV app and the 1131 to figure out the command format and responses, then write your own plugin (or heavily modify the Pioneer Receiver one) to work with it.
Or... you could downgrade to the VSX-1130 which still uses the standard Pioneer command set (based on their Custom Install online documentation anyway).