Was this before or after you removed them?
it is near impossible to diagnose problem without having car in front of you and even then it could be a trial and error situation, the belt could be either too loose or too tight, if it too loose when you turn on a/c and pressure comes on the belt could start to slip and be fine when a/c off, too tight of belt will make a noise aswell, it could be the slipper clutch system inside pulley of aircon that is fooling your eye either, if it slipping you will get a smell of rubber burning,
When you have belt on you want it tight but not that there no give in it, there is no exact measurement for this only experience im afraid but this might be a guide, when you have it tensioned up, catch the belt and you should be able to twist it a bit, not a full 180 degress , but just say belt is in the 9pm 3pm position on a clock, maybe twist it to say 10pm 4pm... hope that doesnt sound too stupid but only way i can think of explaining.
I havnt seen a standard car for a while but isnt there a real flimsey idoler tensioner that looks like it belongs on a bicycle or an EVO

that kinda hangs down on a long adjusting bar in front of timming cover, ive heard of these breaking or giving trouble.
You cant do any damage with belts off, so try experiment when putting them back on, spin the pullies by hand if you can and see is there roughness or noise, and check condition of belts, are the gone shiney, hard, cracked???
When you use a catch can, you will stop all that shite and vapour getting into engine, have a look around the butterfly in throttle body and see whats built up around it, the vapour and oil that comes from breathers is piped into inlet pipe, goes into compressor side of turbo, is pused through intercooler, in through throttle body, in around your inlet manifold and down into cylinders and burnt, it is noted that the vapour and oil will weaken octane in petrol, and tarnish internals of engines, and put a coating on them, ANDYFORRESTPERFORMANCE.CO.UK, Andy recomends it too, and points out reasons for it i think,
there is a bit of messing around with pipes to be done and you may have to buy some piping, T joints, reducers etc, but you wont know what to get till you go at it, there is no set way off doing it, just whatever way suits you and is handiest for you, you probably wont get blanks or stoppers so main thing is when you are blocking the ways into the inlet pipe, make sure to use something that has a head on it and cant fall or be sucked in, somethong like a bolt etc, have a look around and maybe there a scooby specific catch can and fitting kit available from a company, it may be more exp to buy but at least you will have everything and mayb even instructions
