The problem with the thermostat at the front is it has to heat all the way back to the front of the head to open the thermostat... So the head ends up just about cooking....
If you run out of cc's from your injectors you can buy bigger motor bike ones from US eBay... And by doing a google you can find velocity stacks to suit...
Sound like the Ashley manifolds are a hit and miss thing according to Turbosport forum too....
I see you haven't extended your throttle bits yet... Get someone who can TIG well....
I am sure it will sound poo poo hot when it all comes together....