Are you still running a 750 double pumper on that engine? That was the last thing I saw for fuel with a quick search.
If you are, you're not going to have much luck with a carburetor and engine temps under 150. Just the nature of a carb. With a manual choke you can make it work better by adjusting it along as you go but with electrics it's hard to get them dialed in that well. Or maybe that's just me, I haven't been able to do it. I try not to take off until I'm up to at least 160, even there I have to do the heel-toe brake throttle and clutch dance to get it stopped and started until it gets closer to 180 and the thermostat opens. You think yours is cold blooded, my 340 doesn't seem really happy until it gets to 190-195.
Also, if you're running a carb it may have something to do with your stalling issue as well. The fuel in the bowls moves around, if it's stalling in corners you may need to raise the float level a smidge. Do you have an A/F? It would be easier to tell if you did, you'd see it leaning out in the corners. Since you've got an electric pump you shouldn't have a fuel pressure issue. Only other thing to consider would be the unbaffled fuel tank, how much fuel was in the tank when you ran the course? If it was under a 1/4 you might have been sloshing the fuel enough to starve it a bit.
