You want to bridge the pefermance between the viper and the bosx S? there are two ways to do this. One is to drop in the 3.8L 350hp engine from the 987 S or if you want to retain the stock engine this will give you max gains. Not for the faint of heart. 390 hp on stock internals or 450hp if you want to go all the way.
http://www.t-t-p.de/english/986.php