Volvo V70 05' squeaking noise and engine surging.
 

Hey guys this is my first car and I've been doing my own repairs and maintenance to save money but this problem might be too big. I've taken it to a mechanic last week for a quick diagnosis / check engine reading. I am dropping it off tomorrow for the day for a full diagnostics but I'm always sketched out about mechanics and would like some advice.

Squeaking noise coming from the timing belt area. This usually happens after long drives like on a freeway or on hot days. I first thought it was the auxiliary belt but it still made the noise when it was completely off. Can it be the timing belt or some rollers that are loose?
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Engine rpm revving / engine surging often happens when in put it into park or when I am slowing down. It has died on me two times recently when applying the breaks and slowing down. Mechanic said there is a leak and the psi is too low.
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Headlights also surge along with the engine.


Engine codes

PO171 BANK 1 LEAN

PO191 FUEL RAIL SENSOR

PO190 FUEL PSI SIG FAULT