I'm sure I will get a little bit of hate for this but... I was having the same problem on my RX8 like a week ago right after I filled up the tank. before I filled up I was having a rough idle problem, but after I got gas the car completly died on me while driving down the highway, and would not restart... to get to the point after trying a few things myself I ended up taking it to the shop. They ended up replacing the plugs and wires, the coils, and the fuel pump (because they broke it). they also came to the conclusion that the gas in the tank was contaminated, so they drained it (hints the broken pump) and filled it back up. The shop told me that it was a combination of all of the problems together making the car act like it did. when I got it back it ran like a CHAMP (or as well as expected for an RX8) haha. When you take the car to get gas are you going to the same place every time? maybe their gas is slightly contaminated? maybe so octane booster would help?
And just to clarify to hopefully reduce the amount of flame I will receive I have a 2013 wrx on order, currently waiting for it to get to the dealer, I am not just randomly a member of a subie forum.