Confused: Why would fuel pressure increase once the engine is warm? I am thinking you have a choke issue or the carb itself wasn't assembled properly, as much as you don't want to hear that. If you are still convinced that fuel pressure is to blame Summit sells inline fuel pressure gauges for less than $20 that will tell you for sure if your pump is the problem or not. IMO, I once had a mechanical pump Datsun Z22, the pump can't change pressure as a result of engine temp, only engine speed and even that only changes volume. I think you have a mess of a carb there and you should be directing your attention to that first. I bet if you change the pump you will have the same results.