I have a 2013 Chevy Tahoe V8 5.3 L. I purchased the vehicle from a dealership with a custom exhaust and K&N cold air intake. Since I've purchased the truck 2 yrs ago it'* been kicking out codes p0172 and p0175. The dealership had me put the OEM cold air intake back on and they replaced the mass airflow sensor telling me its the K&N causing all these issues. Well code p0172 has resolved but p0175 is still tripping my check engine light all the time now. The dealership is now telling me I should at my own expense pull off the custom exhaust and put an oem on and see if that resolves the issue. Now mind you I purchased the vehicle with these customizations they told me we're covered by warranty now aren't. The resonator is going now. The dealership is not wanting to assist any further and I've got a truck that idles like a beast, sucks gas like a sieve, and sometimes doesn't want to start. Suggestions thoughts?? Could use all the advice and help I can get thank you!

Both codes meant, that the O2 sensor in each exhaust, was seeing a rich condition......

In cases like that, you look for something common to both banks.....in your case, K&N filters with too much oil can contaminate the MAF sensor,and if the MAF sensor data is skewed by this contamination, it can set BOTH codes....

That took care of the MAF problem, when you got rid of the K&N and replaced the MAF.....Now there is no longer a problem with Bank 1....

However, you still have a problem with Bank 2......so now you have to look at problems that will only affect Bank 2, and not Bank 1, that can create a rich condition......the obvious ones are a leaking injector(2, 4, 6, or , or a bad O2 sensor(contaminated)......take a look at both O2(pre, not post) sensors and create a vac elak...if both O2 sensors go lean, I doubt the problem is an O2 sensor...

A good scan tool would show that Bank 2 short term/long term fuel trim is a negative %, possibly around 18-20 or more, while the Bank 1 data is just slightly above or below 0 %......

One thing you might do is pull the plugs on bank two.....the fouled plug will indicate which cylinder is your problem.......or if you have a sophisticated scan tool that shows individual misfires, that will lead you to the cylinder at fault...

I am not leaning towards an exhaust problem.....that can be verified, by removing the pre O2 sensor on one bank and doing a back pressure test, and then doing the same on the other and compare results......