Going single will save you from a lot of headaches, vacuum lines could take forever to trace and replace, too many potential leaks to find. Not to mention going single will save some weight! I don't think you need the sequential twin turbo unless your racing on a tight mountain road like a Touge where you need response in the lower rpm's, this isn't initialD its real life, lol.
RE: I'm going Big Single on my Rx7 FD3S! Project!