VW CC 2012 LUX - FAILING MAF?

Hello all, this is my first post here. I have a VW CC with 96k miles that i have
been driving for a year without much trouble. I recently moved to a new place
and found a good foreign car Repair shop and i gave my car for updating the
Tensioner. Here is when all the problems started.The next day after replacing  
the Tensioner, i got a CEL and they said your PCV Breather is bad and i
replaced it which fixed the issues for 2 weeks. The only thing i observed was
car would take 20secs to drop from 1000rpm to 700rpm in cold start and bad
gas mileage. Today while going to work, it threw a CEL again. I took the car
to scan and found the codes 00257 MAF circulation and 08584 too rich to
idle bank 1. I am confused if replacing the MAF would solve my issue. I dont
know whom to blame here, the shop or is it really that my parts are wearing
out because it's old.