Rough running to 5000rpm

[DfreeGS500]

Hi all, I have a GS500 1998.
K&N lunch box with shorty Delkevic exhaust. Rejected the carbs.

Issue is

Ideal fine and revs fine but when under load, pulling away or cursing at lower speeds it miss fires and runs as if only one cylinder is firing. Open the throttle and it's fine close it off and cruise roughness comes back.

Any ideas please

Thank you

Darren

[chris900f]

What jetting did you use?