tecnigas is a much better pipe. they are both cheap as hell and both will eventually break on you. however the biturbo has a very limited power band while the tecnigas have a very broad powerband. personally i recomend reshaping the stinger into a 1 inch less straight piece of pipe. it will give you even more top end and i noticed no loss in low end.
i used a small section of handlebars for the stinger. the pipe in the pic was not the final mod i went with. went a little shorter on the stinger and made it look better. just dont have a recent pic.
also, if your friends dont know anything about mopeds they might think your "classy biturbo" looks cool, however everyone who knows anything about mopeds will laught at you for being one more jerk with a tomos and a biturbo pushing 38mph.
even un modified it is a way torqier pipe and much better for city riding. if you want top end dont bi a biturbo. there are much better top end pipes.