So I bought a 2008 mustang gt premium on thursday, feb 20th. I test drove it for over 45 mins on the freeway and also through normal daily stop and go traffic and it drove wonderfully. Had about $10 worth of gas in it. So I buy the car and fill it up with 87 regular gas and drive home(25 miles) and runs great. Park it for an hour because of a storm that came through then go to start it and cel comes on. No symptoms so far. Take to autozone and the codes read P0171, P0174, P2195, P2197. I drive about 5 more miles and it starts acting up...like its not getting enough gas. Turn it off for a little while, starts back up and its running good. Drive several more miles, run it slightly hard a couple of times and continues to run fine with the cel still on. Let it sit for 2 hours and starts driving bad again. Basically sometimes it drives great and sometimes it doesn't. I changed the fuel filter and also cleaned the MAF sensor. Here's what I know about the car and what I was told from the dealership I bought it from. Has a C&L CAI, an off road(only has front cats) Hpipe. I know it did have a bama tune before the dealership got the car. They said they took it to ford to reset it to factory settings...not 100% sure I believe them. There could be other mods that I'm unaware of. So I'm thinking its one of two things. Since it supposedly is tuned back to stock, it's messing up because the cats are gone?(besides the front two). Or do you guys think it could still have the bama tune and possibly be set for 93octane fuel instead of the 87 I put in it? What would make it drive great for 45 mins and then after filling it up and 50 miles later start acting up? Any help would be awesome! I really like this car, just need it to run correctly.