It sounds like your distributor still has the big spring on it that isn't done advancing until above 4500 RPM or so twocents
You can check that out by revving it up to over 5000 RPM to check total advance work shruggy I do it on all my motors, revved up above 5000 RPM to make sure what the total timing is where I shift it, some ECU will retard also above a certain RPM scope


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)