IMO, if you expect to routinely encounter altitude changes of 10kft, you need to be fuel injected, if you want optimal performance. Whether that is an IR set up or a 4-barrel conversion is not as material as the ability to actively sense manifold absolute pressure (and other inputs as afforded/required by modern ECUs) and alter the fuel air mixture accordingly. Depending upon your ECU and desires, you can realize a variety of other benefits from FI as well.
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