Fuel trims

What would cause long term fuel trims on one bank be significant higher compared to the other.
Example my car on old tune was running long term 25 percent (max)on passenger side driver was very little. This seems to occur at idle not as bad under throttle.
New (mail order) tune is about 15 to 19 on that side now.
Under throttle long term and short term trims 0 out
At idle short term trims between 5 and 10 maybe less but still more on that one side
I have idling issues it seems to idle fine in gear or park with some oscillation.
In drive when i come to a stop it wants to stall bit catches then levels out. Only stalled once

What are the modifications to the engine?

I'm sorry Ivery posted many times I forgot, I'm going to make a sig.
355 GM847 ported heads with 2.0 1.56 valves 1.6 rr comp, 918 Springs 7.2 pushrods stock lifters , supporting mods, 4l80e 3k stall Dana 60, jethot Headers catted y pipe. Had a pcmforless tune and now a solomon tune and same thing. Tho Solomons seemed to run a bit better.
On a side note will a clogged cat cause these types of symptoms. I'm assuming it might be the extra fuel causing my rear 02 on that side to go crazy

I would think a clogged cat would reduce air flow through that bank of the engine, causing it to run rich, since the fuel is based on air flow through the MAF sensor to the entire engine. That would cause that clogged bank to run rich, and the PCM would go negative on the LTFT's on the clogged side. And, a clogged cat would show up more at increased engine load/RPM (higher numbered trim cells) and not so much at idle, low flow. And cam overlap can promote split BLM's.

You can check for a clogged cat by pulling the O2 sensor and connecting a pressure gauge to the bung. Do both sides and compare back-pressure readings. Do it in open loop so the O2 sensor exposed to ambient air does not affect the A/F ratio.

Faulty O2 sensor, exhaust leak before the cat on the high LTFT side, misfires on that side. What throttle body are you running? Some of the aftermarkets seem to contribute to split BLM's.

When you do a signature (which I always recommend, but it not a popular idea here) include the year of the car.

Thank u Injuneer it's a 97 btw

Would loose a loose rocker or bad lifteright, bent pushrod cause somthing like this?
I hear chattering noise more prevalent on that side than the other.
If I pull the valvecover what should I look for

My car had similar issues when getting tuned. Turned out my alternator was shot

@Injuneer
What is your opinion on this, seems exactly what my car is doing
https://youtu.be/kWX32HZ-aI0

Check this video out
This is an ls1 I have an lt1 but the sound is the same
I'm having issues with my car and this pretty much mirrors the sound my car makes
Is this knock from detonation? Bad spark timing etc?

I never get much out of videos.... 50+ years of loud rock concerts, loud cars and now old age has not treated my ears well. I tried listening with my high end Sennheiser headphones, and all I think I heard was a possible exhaust leak. An exhaust leak before the O2 sensor will cause high LTFT's. You should never hear detonation at idle or no load revs. Cylinder pressures are not conducive to detonation (knock = post ignition). And even if there was knock, the knock sensor should pick it up and pull timing before you can hear it. Most use "ping" to describe pre-ignition, and that's not likely at idle unless you are running extremely low octane fuel or have way too hot plugs.

@Injuneer thank you it was a long night of irritation with the car.
I got a tps code p0122 but I'm unsure if I caused it from probing the wire or if this is my issue.
Car idles rough and idle dips almost stalling coming to a stop. I'm going to change the TPS and repair the wire in was probing to see if that will solve the issue I've been having even b4 of checked the TPS

I found a small exhaust leaked coming fromonths the clamp holding the y pipe and the header together on that side few inches from the o2