Really odd running issue. Backfiring, rough, loss of power

[HeavyMetal]

This one goes above my understanding.

 

Its an 89 MJ with a 4.0L, AW4, NP231.  Ran perfectly fine on a trip I was on, couple hours driving on road, wheeling, so on.  Tried to pull a friends truck out in reverse with a strap, nothing very hard or major,  just one snatch pull with a strap, and from that exact moment on, this issue began.

 

The truck misses, backfires, surges, loses power in huge rhythmic surges on acceleration until the absolute moment it gets out of 1st gear.  Once it shifts beyond first, it runs 100% fine through all speeds, throttles, you name it.

In park at idle, it misses, sputters, and then on revving it, it backfires out the tail pipe, has total loss of power, will not clear out.

In neutral, you can rev it to your heart's content and itll be smooth as silk.  I believe the same in reverse.

 

This is one of the weirdest running issues I have had in 12 years of Jeep ownership and 4 XJs.   Anyone have any ideas?