[YTNUKLR]

1) Mixture & timing makes a big difference. ~12.6-13:1 AFR under full throttle from 4500-redline & solid ignition required to see max power and get apples-to-apples numbers.

1*) It is time-consuming/difficult to get proper AFRs across the board using MFI on "custom" combinations (different cams, ports, etc from a factory config). to give you an idea, you will have the MFI pump on/off the motor, and apart/back together multiple times to get it close for all conditions.

2) I built a 3.0SS (98x66) w/ Weber 46IDA for a street hotrod. We ran it w/ SSI & 1-5/8" headers on dyno (same day/conditions), and I recall it was 230hp/243hp, respectively, on pump fuel. The 1-5/8" headers moved the powerband up by ~400rpm. As it was a pump fuel, street car we decided on SSI. Slight trade on top end, much more usable and torquey for street.

If it's built well (reliable, good leakdown, good compression, no obvious issues) and tuned well (proper AFRs + timing), I would go deep on the cam timing. . . :
--your config sounds like a reasonably "cookbook" hot rod. Similar engines have been done many times.
--"super bike" top end power is the result of highly effective scavenging from the exhaust. This means having a good exhaust and high overlap of the intake & exhaust valves. Your intake is great, your headers look fine (the issue is more obvious when you are using a crap exhaust like SC/Carrera stock manifolds, cats etc.) but, I'd still recommend SSI/factory original heat exchangers for street use.
--RSR Sprint cams have "tight" lobe centers (my measurements ~97deg., vs. 102deg for DC80)/high overlap. This makes a surprising difference. I built a similar 2.8SS MFI w/ DC80 on a 104 and if I had to "fix it" knowing what I know now, I would have run a cam on a 97-100deg. lobe center instead. It didn't really improve low-end torque to have the 104, and it really hurt the top end.

Also, I am not too sure how your muffler works, but I know the factory muffler and sport muffler (based on factory banana) works quite well with MFI.

Porsche knew what they were doing and a '73RSR w/ 43mm ports, 11:1, race fuel, and headers making 308hp IS "top of the mountain" for a 2.8L 911 air-cooled engine.

So, takeaways if it were me, I'd go to smaller headers/HEs, try a stock or sport muffler (factory-style). You're not far away though; I suspect you are missing only about 10%. If you are looking for a super bike feel, I think RSR sprint cams would be next.

Best
Scott