The 45 mm stock pipes and bypass don't yield the power the 50 mm full system does.
It's a three part story. Open air box without the big pipes or ECU doesn't work, pipes without open airbox or ECU doesn't work - it takes all three.
Open airbox for more air in, 50 mm pipes for better flow and more air out and ECU for more fuel. All three, the full kit will yield from 10 to 14 HP increase and 10 lb.ft. torque. And db killers out give a extra big increase of low speed torque from 3500 to 5500 rpm.
The slipon, bypass header with proper ECU will yield less than 1/2 the increase of the full 50mm kit and ECU's are different for the different kits. The slipon ECU is much less rich because of the considerable restriction of the catalytic udder with remains with the slip on kit.
The link below is an excellent narrative and has power curves for the full kit. Notice the big increase of torque at low rpm with the db killers out. Good reading if you haven't seen it before. Thanks, Brad Black.
http://www.moto-one.com.au/performance/s4rsmonstertermikit.htmlIf you look around you can find used 50mm cans and pipes relatively cheaply and you can re-flash your OEM ECU with MonsterMash or one of our board sponsors, sorry I forgot which one. Reflash for less than 1/2 price of the DP ECU when bought separately ($1200).
LA