Mine did this every time I put it in the water. After 5-10 minutes it was fine. Would run fine after that for the rest of the day. I did all the things you mentioned plus pulled off the vst, cleaned out the screen filter in the u shaped fuel line between vst and high pressure fuel pump, cleaned needle valve in vst, replaced in line filter and spin on filter, replaced all fuel lines from tank to pulse pump (3/8“ from tank to bulb, 5/16″ from bulb to pump), also eliminated quick connection for fuel line going into cowling. It’s run fine since.
