The RS2000 4x4 was very much under developed by Ford as they totally lost interest in it themselves
It had a very much delayed launch, and almost did'nt make it into production due to slower then expected sales of the 2wd version, of which I think over 20,000 where eventually sold.
What the 4x4 needs is the 2.3 conversion, the extra torque totally transforms the car and makes it a much better performer all round.
And as mentioned, the transfer box is the weakest link