On this old Aussie/YSi Monaro/GTO from a few years ago, they ran a 90deg and bellmouth for dyno runs.
I can't imagine the 90deg doing it any favours though. Although I'd find it hard to believe a short straight or slight 4" bend would be a restriction.
https://www.marksworkshop.com.au/Pag...oject%2065.htm