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That cart has an Excel drive system, so neither the speed magnet nor speed code 5 will work on it.
The dealer may be required to dial the Speed Calibration set to 30, which will reduce the speed by 3mph and make the 22" tire model have the same speed as the 18" tire model on speed code 4.
You could ask them to make sure it is set for the maximum possible speed that code 4 will allow, which will be around 23mph with 22" tires.