In my 2001 when I put longtube headders there were o2 sensors I replaced the stock 02 sensors out for that read faster and worked with the headders and it seems like you have the same deal....I have so many vihocles with different 02 sensors but from what I remember they were either NTK and I forget the second but I do know its not Bosch..
Have you tried replacing the o2 sensors? As sensors get older they dont read like they used to and although it may seem like a crude way to test their function while in operation is with an OBD2 reader with live PID setting can read 02 sensor voltages......
I remove and clean mine in a shotglass full of lemon juice to decarbonize them then rinse them in a vinegar bath for a few mins then finish them off with rubbing alcohol..
This method works really good for sparkplugs too and saves money on harsh chemicals.......
The upstream 02 sensor measures the amount of oxygen in the engine exhaust that is about to enter the catalytic converter.
When this cross-counting voltage activity drops below a minimum level, the PCM will set the P0153 trouble code.
You can trace the reduced cycling rate of an oxygen sensor’s cross-counting voltage activity to problems that affect either the device, engine performance or the exhaust system. The following issues can cause the PCM to set a P0153 code:
Bad or failing 02 sensor
Oxygen sensor circuit problems from rust stopping proper grounding of the 02 sensor or damaged wires or poor connections at the 02 plugs
A rich or lean running engine
A leak in the exhaust system
An issue with the PCM where you many need internal repairs and/ or a PCM reflash...
First things I do is remove all grounds at their grounding points one at a time clean the spots and replace the hardware if needed...
It might sound strange of a longshot but on my 2001 my mystery issues were started because of a bad cell in the battery.
Car started up fine too....LOL
Good Luck