one plug is to engage the clutch soliniod for the air con compressor and the other is a temp sensor to give you ambient temp reading on your climate control......i think
thats just outright horsepower as in hp...i was always of the understanding that bhp was at the wheels i.e. the brakes.
we also made between 443 and 467 on the same setup using race fuel.....depending on the day/dyno/boost levels.
here's a few of ours
http://image-cache.skylinesaustralia.com/f...2_772_36456.jpg
http://image-cache.skylinesaustralia.com/f...2_772_72199.jpg
http://image-cache.skylinesaustralia.com/f...2_772_78108.jpg