Adjustment to butane conversion

We've been driving our pickup for a bit now on butane and it's doing beautifully. A problem did arise, however, when we tried to flip it back to gasoline. I've been checking some articles online and read that it's adviseable to start the vehicle on gasoline, at least occasionally, to keep the engine clean. It did start on gasoline, but had no power and wouldn't move. It seemed to be starving. Took it back to LP gas and found that indeed was the problem. It was starving for air. If you have this done, be sure to have this problem addressed. I wasn't there for the dialogue on the problem, but apparently the engine needs more air on gasoline. They installed a switch that will open (or reroute) the airflow when on gasoline. We'll probably have someone else look at it to be sure that this is the proper adjustment. Hope this ends this little project. We are very pleased tho' with the performance on butane and would recommend it to anyone trying to save money on fuel. Now, back to life in Belize!