by changing my headgaskets to a metal one will this lower my comp

 

The stock head gaskets are metal . From what Ive been told , you could get thicker ones and lower it a little . Not sure how thick you can go .

 

Doing this will throw the timing chains off and mess everything up depending how much you decrease or increase the thickness by. The only thicker gaskets I know of are copper and they are prone to coolant leaks so are not very good for boosted applications.