Hmmm – if a mechanic is baffled, not sure what to add. I had a Wildstar before my Roadliner. I can’t remember but being as it’s carbed I assume there are no electronics such as an ECU involved. Its clearly a fuelling issue. Sounds like it floods out at that throttle setting? Then, on restart the racing is the excess fuel? Just trying to help but given what you’ve done have we thought about vacuum lines? I removed some emissions control system on my Wildstar – can’t remember what its called(AIS??) – had to put plugs in the heads. Is that still there? Could this system be at fault? That had various vac lines.