I have an 06 Nomad.
I don't know what model the OP has.
On a Nomad, the clutch is by fluid, not cable.
That said, his problem is throttle. On my Nomad, when I installed 4 inch up, 2 inch back risers, only the hoses were stretched out to limit. The throttle cables still had plenty of "play". So, I did not try and pull "slack" from any side, of any guides.
So, what model do you have, and did you pull slack, and if so, from where.
Where are your cables now, in front of, or behind the risers ? Are the nuts tight coming out of the hand grip housing ?
The more detail you provide, the better answers the forum members can provide.
06 Kawi Vulcan Nomad - Cobra Lite Bar, Phat II Risers, Vista Cruise, Krusier Kady, Kuryakyn Longhorn Dually Pegs, Mustang w/ Backrest, Vance & Hines Dual Baggers, PC III, Cobra Luggage Rack, Electrical Connection LED R,B, T Conversion, Jay Stephens LED Tail Light, Classic Chaps, Avon Cobra's.