how much wold a screamer pipe be for a tjet anyone? really like the sound of evos etc and think it would make a tjet even better

First off, you'd need to buy a new turbo with an external wastegate. So cost is already past and beyond any possible gains. (around 600-800 for the turbo). Then you have pipe work to play about with, again, expensive as you will want stainless.

To be honest mate, great idea. Just would require alot of work for very little gain.