The information here,
Is not quite correct.
For maximum power and transitional fuelling AFR's should be between about 12.5 and 13.2. (Individual engines vary a little).
Best AFR for lean cruise in a gasoline/petrol engine is around 15.5:1 AFR.
Only in normal driving & above closed loop enable temp, will the O2's command 14.7:1 (unless the car has a lean cruise mode).
As soon as some parameters are passed, i.e. when you go passed a certain TPS, or the RPM or MAP go above a certain value, the car then goes into Power Enrichment mode. Where AFR's are commanded from the PE table which are set by the factory (usually very rich above 4,500-5,000 as a cat protection feature).
Adjusting these AFR's can give you more power and better response.
http://sdsefi.com/techegt.htm
http://en.wikipedia.org/wiki/Air-fuel_ratio
Changing Throttle Bodies, doesn't always mean more power. IF the TB is a known restriction then there may be some logic to it. Though if the inlet mounting on the intake manifold is the same diameter as the o.e. TB i.e. you aren't going to gain anything by fitting for example a 55mm TB onto an intake that has a 50mm inlet it's not going to do you any favours! You now have a 2.5mm lip jutting into the airflow.
Just fitting a bigger TB, because bigger must be better isn't sufficient logic to get more hp. In a lot of cases they can lose you power and throttle response in the low and mid-range.
Going bigger on injectors needs careful research. Most o.e. injectors will flow adequate fuel for a mild up-grade and on OBD-2 cars the maf-sensor and O2 sensors will enable re-learn of fuel trims in the PCM/ECM.
If the duty cycle of the injectors goes above 80% though, now is the time for bigger injectors. In which case you need to know the flow rate at nominal system pressure and look for something suitable to replace the originals with.
This is one of the better sites for everything to do with F.Injectors:-
http://www.rceng.com/
Bear in mind though, if you change things like TB's, maf-sensors and injectors, the parameters in the PCM need adjusting or the engine will at the least throw a DTC or MIL or worse, will not start and run properly.
Choosing the right camshaft is a science. You have to know first what you want from the car and exactly what you are going to use it for.
Camshfts, cylinder head flow and Compression ratio are interlinked. You'll get the maximum gain when all three compliment each other.
If you wish to fit an aftermarket cam, you then need to talk with a good camshaft company. The term "fast-road" cam means nothing.
You should be aware of exactly what it is and the difference from an o.e. cam Also you should be given the amount of lift, total and 0.050" duration, LSA and valve timing along with valve overlap. All these things should come on a cam spec card. If you can't understand it try asking someone who does and can explain it to you. It's your engine, your money and your interest to know exactly what is what and how it will affect the drivability of the car. Seek professional tuner advice! Get more than one opinion!
As a suggestion try and find the actual specs of the o.e. cam first and then with help decide whether you need to either go for bigger lift (this would mean same basic rpm range but more power within it) or increased duration (moves the rpm range up higher, but has the consequence of losing you power down low). Or a combination of the two.
For general Tech understanding:-
http://www.geocities.com/zeener96/cams.htm
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0606em_camshaft_specs/index.html
http://www.chevyhiperformance.com/techarticles/148_0505_camshaft_basics/index.html
For seeing the effect different camshafts have, as an example:-
http://www.compcams.com/technical/DynoSheets/
This shows different cams used in the
same engine. The three numbers on each graph denote total or advertised duration. The 'H' after the 3 numbers means Hydraulic as in tappet or lifter.
The 'HR' denotes Hydraulic Roller (has more lift with same duration compared to 'H')
This is done on an engine dyno which will usually only pull from 2,000rpm or so. You are able to see how the power moves up the rpm axis as duration is increased, to a point where the engine dyno cannot pull the dyno from 2,000 it has to start higher (big loss of low-down power) but hp is increased much higher up.
For street engines you usually look for the maximum amount of torque from as early as possible and for as long as possible.
