Thanks for all the comments!
I've just sent off my intake manifold and throttle body to be reworked by 'Headtune', they offer the following improvements:
THROTTLE BODY:
Noticeable gains to low and mid-range power can be made by re-profiling and polishing the internals of the throttle body, by allowing more air to move faster into the plenum. Additionally, throttle response becomes ‘crisper’ and more immediate.
• All casting, pitting & boring marks removed & smoothed
• Internally re-profiled and highly polished
• Obstructive screw-ends ground into spindle
• Perfect horizontal opening of butterfly plates
• TPS Advancement
• Leading edge of butterfly 'knife-edged'
• Chemically cleaned
• Fully lubricated
INLET MANIFOLD:
Good gains to low and mid-range power can be made by re-profiling, smoothing, and polishing the internals of the inlet manifold – particularly with turbocharged and high-output engines. Furthermore, engines fitted a badly designed inlet manifold can be improved almost beyond recognition.
All marks left from the casting process are removed (where practically possible) from the runners, leaving smooth surfaces with minimal obstruction to the flow of air. Where part of a runner forms a link between the injector boss and the head, the inside is ‘ribbed’, to allow for better fuel/air atomisation and to effectively make the runner an extension of the inlet port.
The throttle body bore can be smoothed and polished to assist with air flow, particularly to runners that would otherwise draw less air flow and consequently run leaner (thus balancing the power across the cylinders - similar to how individual throttle bodies operate).
All sounds good, rather than buying new manifolds etc. I wanted to maximise what I've got. I'll post up some pics once I get them back before I fit them, and my impressions once fitted and driving with them.
http://www.headtune.co.uk/