UEL install after downpipe & tune.

If I install a header after it has already had a downpipe and tune done, would I need to tune it again?

 

I know the header doesn't change flow that much, its mainly the up-pipe/downpipe that do that. I was just wondering if I was ok with installing one and not having to tune without messing anything up.

I have used the search already, and have found only information about installing a header with a stock downpipe. But where my dp is not and its already tuned for it, I figured the information in those threads are not accurate for my situation.