Hi guys I am looking for some help if at all possible.

I have a 2004 A4 2.0 fsi awa none turbo petrol engine

This past week or so the Car has been jumping in and out of limp mode and it's getting more frequent as this week as gone on, it seems to start once the car is upto temp. I had the RAC pull the codes from the car and these were as follows

17861- Exhaust gas temp sensor. O/C. S/C
17428- Fuel pressure limit exceeded

I have read as much as I can into these codes over this past 48hours until my head coldt take much more. But didn't really get much info with regards to fix's or possible causes.
I rang my local reg garage who I trust but they don't seem to confident in finding out what's wrong with it and said I could end up replacing several parts and still not get anywhere, I just wanted to know if anyone else in the know or other owners that may have had this issue and if so what was there fix for this. Thank you guys for your time