I would recommend buying a scanner for yourself. I got one on Amazon.Com for $80 and it has freeze frame data and live data and it works on all OBDII compliant vehicles, which is basically, all vehicles 1996 and newer.
The main reason I recommend this, is I had 3 different places tell me 3 different things and after I bought my scanner, I traced the problem to something completely different than all 3 places.
All Autozone told me was a random misfire code. One shop told me either the left cat was bad or fuel injectors, and the third place told me fuel injectors or a fuel pump check valve.
With my scanner, and help from the guys here, it turned out to be an O2 sensor.
Trust me... get your own scanner.