My girlfriend has a 2003 BMW 330i that head been sitting for a come of years. I changed the spark plugs, coil packs and changed the oil and filter. I took the battery out of my Durango and put in it and fired it up. I got it to start but I'd have to keep feathering the gas to keep it running. So i went and bought a brand new battery, some octane booster and put a couple of gallons of gas in it. Now it won't start..... what could the problem be?