SwaysLS400

(UPDATE I HAVE SOLVED MY PROBLEM AND UPDATED THE TITLE TO INFORM OTHERS WHO HAVE THIS ISSUE OR HAVE A SYMPTOM OF THIS BIGGER ISSUE; SKIP TO END IF LOOKING FOR SOLUTION) Hey guys, I have a ‘96 LS400 I just picked it up about 2 weeks ago, I had to have a couple things fixed and replaced but since then the car has ran like a top aside from some issues that I will address at a later date. I have been driving the car to work and back (6 miles total) however I was driving it to work tonight and I decided to give it WOT, this is probably the 3rd or 4th time I’ve done it since ownership (mainly doing it to make sure the tranny moves through all 4 which it does fine however I will need a new tranny mount I believe as reverse vibrates when the engine is cold/under power) but when I gave it WOT around 2k RPM the engine starts surging not enough to buck the car or anything but I can hear it because the previous owner straight piped it from the headers; TLDR after WOT my LS400 began to surge around 2k rpm while coasting
Any help would be appreciated especially as this is my first forum post thank you all who stops by!
Edit: I will take it to AutoZone in the morning as I no longer have a code reader but I do have a CEL and I believe it is just for my missing O2 sensor
Edit: Upon searching endlessly on this topic because it seemed no one had gone through a similar issue, I had found an old CL Forum post that described a similar issue to what I was having; surging on deceleration, this post was made in collaboration by LSBob Yamae *will update with links and name correction later* basically if you’re having one or all or some of these these issues it’s going to be leaking capacitors inside your ECU, you can send it in to be fixed or swap it out for an ECU with the same number on the front I will leave a link to a much much more detailed explanation on the problem, cause, and solution by those mentioned above.

CLLEXUSS

Its going to be tough because your car has been modified. And how is this car supposed to run properly without 02 sensors? You took on a challenge, thats fine, but for anyone to diagnose here.. they have no idea what the person did or modified or changed on the car, so yea you got a puzzle there.

sigtwenty

which 02 sensor is missing? pre cat or post cat? if its post cat that wont matter as its just there to detect cat efficiency. but if its the precat that is what aids in air fuel mix and other parameters.

SwaysLS400

I plan on getting an exhaust in the coming weeks so I can remount the O2 sensors, the car is only modified by the cat being removed as the previous owner must’ve sold them for money, because when I rolled up to buy the car they were in a everyday early 2000s Kia that also happened to be missing a cat for some reason 🤔 but yes I understand it’s going to be tough was just wondering if other people could have had the issue, O2s or not.

SwaysLS400

Im wanting to say just the post-cat O2s are gone but when I had it on a lift I did notice it was cut a little further back than it really needed to be but i will edit this post in the morning to let you know. I really appreciate the response

SwaysLS400

Drove the car about 30 miles 15 to and from, I noticed that with the AC on it will not do it at all, even from a WOT pull
Took the car to Advanced and got these
P0141 (O2 Heater Circuit Bank 1: Sens2
P0100(MAF which I disconnected to troubleshoot and the car will not run without it at all)
P0110(Intake Air Temp Sensor 1
P0161(O2 Heater Circut(Bank 2,Sensor2)
EDIT:forgot to mention it seems all Pre-Cat O2s are all mounted