Erm...too many threads, you need to read up on this, ClubProtege.com has lots of good info...
Anyway, B code VAF from 2nd gen RX-7, I got mine for free(2 of them) but I bought a different one(a P code from a Capri Turbo) for $15. People have gotten 8+ WHP from that alone.
Cone filter...might be able to piece together an exhaust pretty cheaply...