It has a 2.0 liter, I-4 with unknown mileage.
The CV-joints and motor/transmission mounts are new.
Sometimes, in all gears, it will refuse me torque for a few seconds without actually popping out of gear (The engine will rev up as if in nuetral; and then, it will return to normal.)
It frequently jumps out of fifth and reverse gears.
If I hold onto the stick while accelerating in fifth, I can feel it jerk out for a split second before resuming to speed up.
Will greatly appreciate some troubleshooting tips. ...

When I bought my 1993 G20, I was going full bore for fuel mileage even to the point of changing out the transmission fluid with synthetic.

Big mistake.

The transmission is made for the lubrication of mineral oil and within 20K miles it would no longer stay in fifth gear.

I ended up swapping the transmission with another from the bone yard.

Hope this helps.