Newbie here...

I have a 2003 Audi A4 1.8T Quattro. The engine is sputtering in idle and there is a loss of power.

I recently had the codes checked and they are as follows:
P0171
P0300
P0301
P0302
P0303
P0304

I changed all 4 spark plugs, and the problem persists.

I am wondering if this has something to do with it:


Or under the passenger seat, this part of the exhaust system is frayed:

It sounds like there is noise (exhaust leak) coming from this area.

Any ideas on what to do and what the cost may be to bring it in?