Volvo Air Mass Meter

An actual diagnosis of the original problem (rough idle/running) was done by the shop that subsequently installed the meter. According to the invoice, what they did included:
1. Check rough running and check/clear codes ($24.48)
2. Check fuel pressure (OK) ($48.95)
3. Check/clean/repair connections at the air mass meter, car runs bad ($24.48)
4. Replace AMM. Test drive and cars runs OK. ($48.95)
I was then told that the only two AMM's they had were priced at $375 and $250. I said I'd like to try to find one for less. They said they would install it (I've been a customer there for about 15 years and they do offer used parts when available). They recommended I buy a Bosch part and gave me the part# to look for. I was able to find a new reconditioned Bosch part in a factory sealed box for less so bought it and took it to the shop to be installed. This is the part that was in the car when I picked the car up and found it was still running rough. I checked with the guy I bought the part from to see if he has received any other complaints. He said he has sold 14 of the same units in the last few months and has not had any issues. He said he acquired the parts from an OEM warehouse which had closed. Thanks for your reply.