Suggest putting an OBD2 reader on it to see the fault code(s). That's what they're there for.
This, plus: When was the last time you put fuel in it? Was it sat for 4 months with aging fuel? If you don't get anywhere with the faults codes (I bet it will be a P03xx misfire) then I'd try draining as much of the old fuel out as you can, bunging in a fresh tank of E5 and taking it for an Italian tune up, especially if it's a P0300 random misfire.
If it's a specific cylinder indicated (P0301 is a misfire on cylinder 1 etc) then coil packs and plugs would be next on my list to check.
