You could try it. I'd reset the ECU and add very small amounts of propane. If there's some way to have it come on gradually as you step on the throttle would be the best. If done in small amounts the ECU may just correct for it and inject a little less fuel. The problem is as soon as you run out or your propane system ices up then your ECU may throw a code thinking you suddenly got an intake leak or something.
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