The GT25 will spool probably just about instantly, because they are so tiny. Unfortunately, your probably looking at about 250 hp tops with those turbos, regardless if you run 20 psi. Btw, twin turbos doesnt mean double the hp either. CFM is CFM regardless of how many turbo's there are. Twin turbos are pretty much a waste of money imho since they make no more hp than a single turbo. Why do you think supra's convert their twin turbo's to single?
Personally, I would go with a T3/T4 single turbo which is more than enough for your 3.1L. Youll make full boost around 3,500-4,000 rpms and could probably make about 400 crank hp on about 12 psi.
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"The CEG Nazi"
www.contour.org
1996 Ford Contour SE - Sold
3.0L V6 and Arizona Dyno Chip Turbo Kit
364 whp, 410 wtq @ 16 psi and only 4,700 rpms.
1999 Tropic Green SVT Contour - Bone stock and MINT