Hi Bob,
Do you know if this MTH J1e came from the factory with PS2, or is this a conversion from PS1? Can you give us the MTH product number?
If this is a factory PS2 engine that has had its motor and gearbox changed than we shouldn't have much trouble calculating the correct tach strip to get the size to synchronize the speed and chuffing. However, if the motor is not a 12 volt motor the PS2 electronics may not be able to supply enough current to ever move at an acceptable speed. Before you spend any money on other potential fixes, please give us enough info to really understand your situation.