hey people i recently got a set of sonics from a fellow frogger for my 12.
had the surface of the extractos milled smooth then went to the exhaust place to have em fitted up and reason for this is that i have custom exhaust already and they made that exhaust.
They said that they wouldn t fit even thoguht they dindt put em on the head .
the reason they said is becuase the 2 centre ports seemd not to line up properly with the gasket i think they had gasket wrong way aroound. There other issue is the standard 12 manifold gasket doent cover all surfaces of extractor face i think this not an issue use high temp silastic .
Shouldi seek other exhaust place or they got it wrong.
There were concerned i think that another 12 owner took some there had em made then they were wrong for a 12. They remade some fitted them up and realy stuffed about ot fit em i think they scared .
The sonic shold be not a prob to fit but are there much advantage to these extrractors yes motor is modded and manin exhuast also .