Ooooh this could be for a number of reasons. Is the pressure regulator freaking out from the increase in temperature? Check to see if your throttle stop and return spring is going out of adjustment. I should be up to speed on your install - but are you using the stock air cleaner or an open element? Don't know if it would cause this issue, but the Weber pulling hot air from the engine bay isn't optimal. It's not dieselling/running on or detonating so that is promising. When you get those symptoms you'll need to look at fuel pressure and coolant/manifold/intake temps. Other than that...