Well is has taken some doing but here we go.
The Sirion before 2005 had quite a few versions.
Basically though there were two air filters for the different Models.
The basic engine (1300 - K3-VE2. 101bhp) has a paper air filter.
The part number for this is 1780197201000.
The Rally 2 & 4 has a Free Flow Air Filter.
(1300 - K3 - VE2. 107 bhp)
Part Number DACC2511.
I hope to put a picture of the two filters side by side on this site very soon.
And I hope this helps you lot asking the questions about this.