the afore mentioned product if you actualy read the instaltion guide states that you have to splce in the wires. nothing that you have to spice the wires into can physically alter the programing of the ecu hence meaning as petrified rabit saysgeneral rule of thumb goes if you have to splice something like this in it's a complete ripoff a gimmic that does not workthis is all 99.9% of these power bosters are is a resistor that alters the resistence of the MAF sensor tricking the ecu into thinking that the air is going into the engine is colder (more dense) or faster (compressed) than it actually is.and what if your paying $89 for a $1 resistor in a fancy box?and again there is a multitude of sensors that will pick up the fact that after combustion there actualy is not the same amount coming out as there is going in so like petrified says the ecu will automatically correct the fueling in line with the amount of gases coming out the other end.that resistor only tricks the computer to add fuel to get more hp, well until the o2 or knock issues cut the fuel back again
ALL THIS PRODUCT WILL DO IS MAKE YOUR ENGINE RUN RICH FOR A SHORT PERIOD AND THROUGH UP ERROR CODES this product will also cause damage to your engine as when an engine is not combusting corectly it will clog it up reducing performance.
as for the air filters if you do the reserch into these products they are purely a plocebo (sorry if thats spelt wrong) effect lots of noise oh geez i must be going faster. as you said you could fit platinum plugs (again look at the reserch until you have done serious upgrades this will do ziltch) combine these with an uprated coil-pack and all you are looking at is a melted piston again serious internal upgrades need doing before doing those sort of upgrades. as for fitting high flow injectors all well and good however 3 things to consider 1 the fueling is controled by the ecu so will still only inject the corect amount of fuel as the o2 sensors would pick up an overfueling and correct the injection time acordingly 2 you would need to uprate the fuel pump possiblely to cope with the incressed fueling or you may find that you will starve the engine and finaly 3 even if both the 2 previously mentioned points do not happen you will again be running rich which will cause incorect combustion as you are still are not adding more oxygen into the mixture hence clogging up those nice shinny new injectors, valves cat damaging the o2 sensors a multitude of bad things.
as for the underdrive pully i am un-famillar with the paticulrities with doing this modification however understand the principles (if i am wrong feel free to corect me). the greatest kill in an engines power is that of unsprung wieght (anything that moves via the engine) i.e wheels pullies fly-wheel e.c.t reduce these wieghts and you reduce the amount of effort it takes for the engine to turn, now this does not actualy create more hp but more whp (wheel horse power) the engine still produces the same power as without the reductions in weight however that power is transfered to the road more effiencently.
if you are looking to get the most out of your engine for the cheepest possible and this is exactly what i personaly have done is to purely give the engine a overhaul. clean air filter, fuel filter, fresh oil + filter, clean the coke out of your manifold ( the black soot built up internally thorefore constricting the pipe reducing the airflow out. air goes in air must come out after all), clean/replace stock injectors, fresh spark plaugs and ht leads. i have a local test run i do after each "power" mod i have done. before i done the works was hitting 82mph after was hitting 88mph for the cost of a new air filter oil filter oil spark plugs and ht leads. sourced the parts from local parts store for all in less that 40 gb pounds.
rule of thumb (sorry to keep saying that) IF IT SOUNDS TO GOOD TO BE TRUE IT NORMALLY IS