[Alan Roehrich]

Several things are possible.

As already mentioned, it could be brakes, however, it's not likely with your description, as less brake would mean less load. It wouldn't bring the secondaries in at a lower RPM, it would just push through the lights.

It could be a converter problem, if the converter has failed and is tightening up, you need more throttle to get the same RPM, and it pushes harder as well.

Or, the secondaries could have gotten looser, either from the spring getting soft or out of adjustment, or if you still have the choke pulloff, it could have gone bad. If the choke pulloff is there, and still hooked up to the secondaries, like it should be, it helps keep them OUT, unless it has failed, then it allows them to come in earlier.

Check the carburetor, then in a safe area, do a flash test, just mat the throttle from a high idle and see if the converter still flashes like it did before.