1985 245 NA US spec

Problem = When started 1st time of the day or after 10-15 hours engine starts and idles perfectly at 750-800 rpm. When load is applied to start out it will stall unless engine revved to about 2000-2200 RPM. After driving for 30-60secs everything is normal (mileage great, driveability great, etc) until shut down and allowed to sit for at least 12 hours then same problem occurs again for first minute. I can be driving or just letting it idle and the problem clears in the first minute.

Background - This started just after I had a main fuel pump failure and replaced the in tank and main fuel pump (about 6 months ago). Both of those pumps are working fine. Problem is not related to fuel tank level and engine does not have time to get significantly warm during the first minute. Problem does seem slightly worse when OAT is less than 45F (where I live it never gets less than 35F) but still is present even with OAT 70+.

I did not replace the fuel pressure regulator. I have since replaced Distributor cap, rotor, ignition wires and plugs (the were due for replacement)and that did not change the problem.

Since I am used to it this is not big problem but wondered if anyone on the board had a similar problem or has any suggestions for a fix.

Thanks
Howard