Gilera Dna / Stage 6 pro replica exhaust rollers

Hey guys, just fitted a stage 6 pro replica exhaust to my dna after my Leo vince gp snapped in half while I was riding I've got the 4.8g rollers in and uprated jet to suit the gp. Im not sure what I should do to make my bike run properly now. When I try to ride it it barely pulls away, when it does pull away it reaches about 30mph then the revs just drop!! Any help will be greatly appreciated!!! Cheers all!

 

lighter rollers

 

Cheers mate, bought a set of 2.5-4g rollers hopefully that should sort it out

 

iv got 4 gr in my aerox but that's a minereli l/c engine and there a bit too light for my liking so im going up mine to 4.2 gr