Fitted 'Racing Reed Valves' - Loss Of Performance!

Hi. I'm new to this forum, and I was hoping that someone out there could help me with a problem I am having. I fitted some 'Racing Reed Valves' to my Benelli K2 100cc 2T. It has a Minarelli engine (Stock), the same one that's used in the Yamaha Aerox 100cc I believe. Anyway, I fitted these for the first time ever, and it has actuly decreased my performance. I've lost a little acceleration, and lost 10mph on top end. I fitted them exactly as the stock ones came out. The only thing I did not do is fit a new gasket, as the stock one looked fine. The reeds I installed where 6 valve ones, while the stock where 4 valve ones. The power-band or power-range isn't as harsh anymore, it seems to be holding back. I even tried lighter rollers and a spare new-ish belt that I had lying around, no improvements. Any ideas people?

So far my mods are;
Exhaust System
Open Air Filter
Re-Jetted
Racing Variator
Lighter Rollers
2000 RPM Clutch Springs

Edit; Sorry, just realised I'm using the wrong forum page. :/

 

Air leak? See what it does with the old ones swapped in again before doing anything else. Just reeds alone usually wont do anything for power let alone reduce it lol