Well about a year and half ago my buddy had a CEL on his 06, but he had some type of flash done (not sure if it was tatrix or what) so I plugged mine in and read the CEL that was all it would do as far as that. Then we took a drive with mine plugged in to try and "monitor" it since he had no gauges. It would read all parameters, but not long any. And just for sh!ts and giggles we tried to flash his after I unmarried mine, but his ECU was locked by his previous tune. So Im kind of speaking from experience, but I havent updated or looked for updates since then.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX