Clutch springs slowed bike!!

Gday guys,I just fitted: so called heavy duty clutch springs but I think they made my bike slower!!!??,The standard ones were thicker and seemed to have more tension too.The bike use to have a powerband of sorts now is just one speed unlike the way it felt before,I thought these springs would improve my bike but I think its made it worse!?.I cant put the old ones back in as I stuffed one up(stretched it) trying to get them out,I paid $20.00 AUSTRALIAN for them and personally think they are rubbish!.I put a power pipe exhaust on,Advance timming keyway,these clutch springs,sports air filter,new reed valves(standard) + runs the standard carby,6 tooth front+ 68 tooth rear,I dont know If I should maybe try get another STOCK clutch spring for the one I ruined and put them back?.What do you guys think?,what other mods do you recommend I do next?.
We moved the position of the carby needle to let more fuel in today,seemed to help a bit= but my bike seems to suffer from the power SURGING(really badly) at high rpms(only)??? we have been through everything but are at a loss as to why????????????.My bro thinks the on/off tap's rubber is stuffed and not letting in enough fuel?? HELP