which header would be best for my stock d16z6, 4-2-1 or 4-1 ?

 

Depends on where you want the power. 4-2-1 would give better midrange power and 4-1 would give better high end power. On a D-series, you won't feel much though, so don't get your hopes up.

And next time, please search, this has been covered hundreds of times.

 

new at this dont know where to search

 

There is a little link at the top of the screen that says search. Click on that and then enter what you are searching for. In this case type in "Headers". Then it will pop up all the forums that have "headers" in the body of it.

BTW, Welcome to HAN.