Exhaust and tuning

[Vollan2003]

Hello, as we all know mods for the rather uninspiring 1G-FE are pretty limited compared to other Toyota engines. Nevertheless I’m currently looking for a new manifold for my IS200, and I want a manifold where all 6 tubes go in to one 3inch pipe. But I’ve only managed to find manifolds with a 3-2 setup, so is a 6-1 manifold something I have to get custom made? Otherwise I’ve found a manifold made by an Australian company called DKNE, it’s a 3-2 with a unique setup unfortunately I have not found anything on this company since 2010, does anyone know anything about where one might enquire that manifold?
 

Now, I am removing all cats on the car, what sort of power gains am i looking at by removing them. And can the car be tuned(N/A) to run more power than what it would get by just removing the cats?

lastly I’d like to know if it’s possible to make changes to the ecu so the electrical throttle body opens and closes simultaneously with the mechanical throttle. 
 

All help is appreciated, Andreas.

[MattDH]

I'd have a chat with these Marc, they specialise in these cars https://www.soarsperformance.co.uk/