Powerzone 421 extractor compare to hotbits 421 extractor is it smaller in piping diameter, and the method of joining from the 4 pipes to the 2 pipes, obviously their design emphasize on overall performance (maintain drivability at the same time provide smoother air flow thus better performance), I try both powerzone and hotbits extractor on my previous engine, yes, hotbit provide better pulling power after 4000rpm while powerzone provide smoother power in wider range of rpm. but frankly speaking, powerzone abit pricy (RM450) compare to hotbit (RM340).
ethanphoon592, you are right, it all depend on the extractor design, last time I join WISE club TT, I saw on wira 1.3 fitted with 4x1 extractor (dunno wat brand but from my observation it is stainless steel, smaller diameter in piping, owner car with bullet plus s-flow muffler), I try to step on this gas pedal, surprising below 3000rpm it is more responsive then powerzone 421 extractor, his extractor design from the 4 pipes join to 1 pipe length is very long, until reach the connector of single pipe of conventional 421 extractor (are you try on similar design extractor?), but to be surprise, this 4x1 extractor after 3000rpm so so only