@almeragt is car owner, he knows most aswers.
It has z32 mbc with BIG D2 front brakes, full race rally suspension, full chassis rebuild. This car is no joke. Owner might start a thread and show pics and setup.
3.5" can be purchased at stores that sell pipes, bends, etc. Aluminium, stainless steel.... whatever you want. Or check eBay whats there. Pipe was modified for MAF sensor and we welded velocity stack at the end.
Car made +14hp over stock intake manifold and held power all the way to 8500rpm (rev limiter, stock valve springs).