Not sure what to do

[Haewn]

Hey guys, I've had my 2004 Aristo since march of this year and the previous owner sold me his car with a downpipe he wanted to get installed. To preface, im a very new car enthusiast so explain things to me as if I am a child, thank you.

The one he gave to me was this one : https://autobahn88shop.com/products/toyota-supra-jza80-2jz-non-vvt-1st-stainless-front-pipe-decat-right-drive-only?srsltid=AfmBOoqPxUyZ9VfydfqiCItw3TiSBrjszbBnZUU3TAiHijk8r0WwDbsS

I gave it to the shop and they told me there should be a block off plate for the secondary holes and people have told me to weld a block off plate onto it as it doesn't come with one. Other than a block off plate, what is supposed to be attached to that?

I am also worried about boost cut and still trying to learn more about tuning my car and all that. My current set up is GReddy FMIC, TRD mufflers and thats it. If I were to put that downpipe on along with a HKS superflow intake on, would I need to tune it then? Please send advice, I wanna make more boost and noise out of my car without being a menace. I just wanna make sure I am doing it the right way and not gonna run into any problems. 

THANK YOUU

(pic of car for attention)