cat replacement pipe
the cat is easy to remove 2 bolts and a u-clamp, if you've got a set of ramps 20 mins maximum provided they're not siezed of course, shouldn't be a problem on a younger car. as for the 100sx - i'm not sure if a direct replacement is available, try www.magnex.co.uk or road runner motorsport on 0115 978 1173, if not, it should only take an engineer or someone handy with a mig welder half an hour to knock one up, use your existing cat as a blue-print once you've got it off.
the perormance on my car has definately improved, i'd say it's worth about 5-6 hp on the hgt, well worth the money, the farty noise was traced to a loose baffle in the mid box, i probably did it when i got a bit handy with the hammer when taking the cat off - oh well, looks like i'll have to have a complete system after all, what a shame, good excuse to tell the girl friend!
hope this helps
dom