Like Forest said, powering the electric choke off ANYTHING wired to the ignition will drop power to the coil and act like a rev limiter at about 4000-4500 rpms. The ignition needs a full 12v to work properly, which is also why one shouldn't use the ballast or the '74 resistance wire. Use a hot wire off the starter, alternator or run a dedicated switched wire off the fuse block to power such accessories.
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