you need a stand alone ECU (which is included in our kit)
1 throttle body = 70mm diameter, ie you can get a certain amount of air through it, plus you then have the length of the inlet
4 throttle bodies = 45-48mm each, but you have 4 of them whats your "total" throttle area now?? MUCHOS bigger, plus your inlet length is now muchos shorter = good
simple explanation, but gives you the basics