[Xeen]

Yikes well if 2/2 times you filled up with mid grade it died then I would say it's a good bet that you will need to run premium only gas.
Try putting a bottle of octane booster in it and if it runs without an issue then you know you need to run premium only gas.
I can't remember did you install a canister style filter, if so pull the canister and look at the filter and see if it's dirty as hell, if not it's probably the grade of the gas.