Ryaniaie 737-230s engines

I have been doing some research into the 737-200 for my soon to be new web site thats when i get time off work, anyway when Ryanair took over some of Lufthansa -200 they had the modified pratts installed i.e. hush kitted, the one for definite was EI-CNT
http://www.airliners.net/open.file/100030/L/
In the old news of the world scheme.

Now somewhere along the lines it has reverted back to the standard 200 type
http://www.airliners.net/open.file/759878/L/

Why was this done, fleet commonality, as you would think that hushkitted -200s would be friendlier at our noise sensitive airports, anybody with inside info?

Cheers

Andy