hi, welcome to the club of frustrated throttle-bodi-ers.
for a throttle body conversion you need several parts (manifold, bodies, etc) which a few companies claim to provide. The only kit Im aware of in the UK is Weber Alpha and they supply prima racing only. Prima claim to do a conversion for £2.9k but will simply not give me details on the conversion. when asked some simple stuff about changing the fly by wire throttle on the cup (or mk2) I got a prolonged doooh type answer. not very inspiring. The business for throttle bodies would be a good quality 172-specific manifold + jenvey individual throttle bodies. Manifold is not available and every time I talk to Jenvey Im told its any minute now (been like that for 4 months..). In addition to that you need a proper ECU. Forget superchip and the likes, even forget a Unichip although that can theoretically control 4 injectors. You need a proper ECU like Omex, or even better Motec, etc. and thats about a grand.
Sooo, £2k parts and ECU + labour + vat and youre lucky to spend less than £4k. Even if you are, nobodys actualy developing this stuff, and I am convinced the various companies were talking to will not develop the kit unless they see demand from at least half a dozen serious people.
So there it is: we get 6 people to put down a £1k deposit and agree to pay £3.5-4k. Takers? Otherwise, Roamer says hes got TBs being developed over the next few weeks, so keep an eye out for him
On what throttle bodies are blocko, BenR or another technically minded guy can give you all the details. In plain english, if you look at your cups engine from the front, the air filter connects via a black pipe to a single metallic part that has four arms and sits on top of the engine. Basically air goes through the filter, the black plastic hose, through a single opening which has a butterfly inside it. when you open the throttle, you open up the butterfly, which lets more air into the engine fed through each of the four arms - one per cylinder. That whole metallic piece is a single throttle body, and it does a fairly ok but restricted job at supplying the engine with air (i.e. power). With individual throttle bodies, you scrap that single throttle body and replace it with four individual assemblies, each supplying significantly more air. The injectors are also often replaced with higher capacity injectors to push more fuel in order to compensate for the increased air intake. More air, more fuel, more power.