well i feel real stupid i have completed the 07 gti build and i am havein problems well my head unit is a alpine iva w200 and i am usein a pxa h701 with it tru a i net so the sub out put into my audiocontrol mvc i had to put a y splitter for the input of the mvc and the out put to each of my mmats 2100.1 x2 and every time the bass hits i would hit hard the first time then go soft the hit hard again an so on ......