Cheers S13eater.
I agree with the principle of reducing ANY restriction, I've always had the opinion of "look for the weakest link", hence wanting to keep the bigger manifold. I know the standard SS1 exhaust is better flowing than the Silvia, so I'm not looking to change that now, I will however install a new cold air intake.
This is the manifold as it is, you can see how the compressor will foul the dizzy.
Anyway, I need to swat up some more on my options for an aftermarket ECU, and see how much I can justify spending (and then spend double!).