PIA 11.x is a slighlty updated version of PIA11.0. PIA11.0 itself is not an official and validated version of PIA. The last official version of PIA is 10.0, which is available at the ISO Data Centre homepage.
PIA11.3 is patch to PIA11.0. The modifications in PIA has been done to better calibrate the C100 and C200 detectors, but not the others. The new feature of PIA11.3 comared to PIA11.0 are the following:

1.) New bypassing skylight correction (new routine and new CLAG files) for the C100 and C200 detectors (see the report by Cs. Kiss & U. Klaas).
2.) New effective solid angles for the C100 and C200 detectors (see the report by P. Abraham, U. Klaas & Cs. Kiss).
3.) New FCS power calibration (as of 2006 October, see the report by U. Klaas).
4.) New transient correction for C100 (P. Abraham, Konkoly Observatory)
5.) Correction of some minor issues and bugs