HELP - Mazda 3 Forum

So I have recently taken my speed 3 out of storage and am faced with a problem. At 3500 rpm with half throttle boost completely cuts out then returns at 4000rpm. This happened a few times then I got a P0304 code for cyl 4 misfire. So I changed all four spark plugs and the coil pack on cyl 4 but I still have the code and rough idle as well as boost cut. Swapped coilpacks with another cylinder and still got the code for cyl 4. What could the problem be??