My 1990 with a 4.0 and 5speed will try to stall when it's in reverse. I've seen plenty of posts with autos having this issue, but no manuals. And no it's not my lack of skill

 

Does it try to stall as soon as you select reverse or only as you start engaging the clutch?

 

Only when engaging the clutch

 

Then I have to say that it's you. AFAIK there's no connection between reverse and the computer or anything else that would alter engine function, but if you wanna eliminate the possibility just disconnect the reverse light switch at the trans and see if there's any change.