just found these are they worth buying 

 

http://scoobyworld.co.uk/catalog/product_info.php?cPath=47_213&products_id=3372

It'll take some weight away from the engine so it can spin up easier/free.

Best analogy I can think of is try to spin a 5kg dumbbell and then do the same for a 2kg dumbbell.

Not really unless your going big power

I'd say was worth getting as said less weight really which in turn should be less strain on the crank :) 

thanks all

im going to buy this to go with it mite as well do it all in one go

 

http://www.ebay.co.uk/itm/330928171495?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I would advise against lightweight crank pulleys , the stock one is to dampen vibration , adding a lightweight one will let your crank wobble, I suggest buying a "fluidampr" pulley , There expensive but they work. Especially if you like to rev your motor

Some may argue the facts, but I'm going with a fluidampr over lightweight ,,

Edit , some may be using lightweight pulleys without problems , but its not worth it for the performance gains

need to match it with light weight fly wheel or its pointless

Do you loose a bit of torque with lightweight pulleys ?

Yes you do loose torque at low rpm had billeted pulleys and flywheel on my old gti6 and was a ****** to pull away and the idle was so unstable I couldn't bear it any more so put all the stock ones back on was so much better to drive. Also they can cause premature wear to bearings on the crank