95 gt backfire/lean pops

So I installed a new clutch, motor mounts and threw on some longtube headers and a catless hpipe while i was in there. the car ran fine before the longtubes, but after, ive got lean pops during closed loop operation but it goes away during moderate and heavy throttle.
the car is all stock from throttle body to oil pan, only mods are smog delete, pulleys and blocked egr valve.
so far ive checked for vacuum leaks and found nothing, triple checked my plug wires and all is good.
things i havent checked are timing and fuel pressure as i dont have those tools at my disposal yet.
I was curious if anyone has had issues like this after longtube install. im thinking non foulers for the 02 sensors may help and will try that afterwork.

It's not going to be a happy camper with no cats on there. Not only will it most likely run better, will for sure pick up torque.

The T4M0 does not react as well to mods as the old A9L. Likely need to chip and tune it.

O2 sensors now too far away to operate properly? Also cats, should run em

What bothers me is that in theory, moving the 02 sensors further down the line on my car shouldnt affect anything as the 02s were pre cat on the original exhaust. i'll try the non foulers tonight as well as check my KOER codes tonight in case theres some dormant codes

update for those interested, put in a catted hpipe and sparkplug non foulers. car backfires still, less dramatic with the cats as sound dampeners. pulled codes again and found codes 57,58,72,311 and 314.
i fixed codes 58 and 72 by cleaning the maf sensor and codes 311 and 314 are due to the removal of the smog pump and associating lines. I'll be switching back to shorty headers and hpipe as i suspect possible the 02 extensions may be faulty. still dont understand why there are no lean, rich or 02 related codes.

its been awhile since i posted as i was working through all the diag. anyways for those that are interested, i ended up checking vacuum and found a few small leaks. repaired sone and eliminated other unused circuits and best i could get was 16in.hg of vacuum. i also found one of the new o2s to be faulty with some voltage drop at the connection so i fixed that but during the diag of the car i bought a semi built engine to throw in the car as i was looking for heads anyways and found a good deal on a long block. based on the findings with the vacuum being low i had suspected the lower intake gasket on bank one to be split and when i got the motor pulled out i confirmed it. between ports 2 and 3 the gasket was split.