I think you should be advised by a performance tuning expert before spending any money. I am not one of those, however these are my thoughts.
- You will not achieve a greater amount of air by placing the cooler in a different location, in fact I expect it would be reduced. The heat exchanger requires a clear air path for air to flow quickly through the fins. Any obstruction behind the cooler will impede the flow of air, reducing it's efficiency. This is why there is nothing directly behind the existing design.
- Although intercoolers are beneficial, the speed at which air is passing through the cooler causes only a small increase in power. Imagine a virtual feather passing through the system. It passes from intake through to the combustion chamber very quickly.
- Any alteration to the length and diameter of the intake tubing will alter the pressure dynamics that the current engine is designed for. You may harm the turbo or the engine.
These are just my thoughts, something for you to consider. We have engine building members, hopefully some of them may care to guide you on your quest for power.