-If this was mentioned before, I apologize ahead of the time, but I want to make a list for the "Mod List" Im completing.

I recently just changed my Bank 1 Sensor 1 O2 Sensor. Before changing it, my car would idle from 500 to 2000RPM and fluctuate throughout. It had rough shifting and whatnot (throughout this problem no CEL light was present), and then it finally came on. Went to local autopart store and got it read. Changed out the 02 sensor, and damn I felt the performance back. When I installed the Intake and Spacers, I didn't really feel a drastic gain, but after replaced the sensor it changed the whole game.

My question is what else parts could be a potential hazard to performance? As in, replaceable parts without opening the engine itself.

Currently Replaced (Stock Parts)
100K timing belt service
Replaced BOTH 02 sensors
Checked all exhaust leaks
Synthetic Oil/Seafoam
Spark Plugs

Thanks in advance!

 

brake calipers siezing
weak/heavy battery
un-reset ecu after mods being done
dirty CAI filter and cabin air filter
broken AC clutch
dirty intake manifold
dirty egr

 

^Correct, Instead of the brake calipers seizing, everything else is done. Forgot to add those to the list. Thanks!

 

Coils, plugs and cat are about all thats left that would.

 

How much did the sensor run and where did you get it?

 

Clogged fuel injectors, dirty fuel filter. Less fuel, less power.