Sputtering by under load/fuel gauge drop

[Makima_xj]

Hey y’all. I got a 98 xj sport I just did a 98 TJ 4.0 swap with that has 103k on the new motor. Everything went smooth but I’m encountering a fast off/on drop in power or a sputter under load during low rpms (2k and 20mph and under)on my last 2 tests up a fire road. Stop start hard acceleration and city/highway driving hasn’t caused any problems. I replaced my distributor cap/plugs/wires and during my second test today I noticed when it sputtered the fuel gauge temporarily dropped to zero (I had half a tank) which went back up after 20 seconds after I turned around and went down hill.
it’s the same pump from before the swap that never had a single issue with and I’m trying to diagnose other reasons for the faults before dropping another $150 on a pump since I’ve been bled dry on this home swap

 

[RCP Phx]

Way to many possibilities without doing any testing! I would start with a scanner that can log data in real time.