I run their kit with a dyna ignition. It raises the rev limiter 400 rpm's, which is truely all you need for a built 400ex, the white brothers and most cdi's are overkill because your bike starts dropping off in hp around 8000 rpm so that is where you ideally would want to shift not at 10,200 rpm. Plus white brothers and many others on the market are just an xr250 box that makes your bike hard to start, dyna doesn't do that.
2001 Duncan Racing National 440ex
Power Cylinder 4000 12:1 JE
web cam 463/9i, port & polish, 3 angle valve job, hardend rockers, titanium valve springs.
Duncan Racing Fat Boy 4 Exhaust
1mm oversized blackdiamond intake and exhaust valves
15 point gusseted frame powder coated candy apple red
Doug Eichner Signature Series Edelbrock Carb
Procom CDI ignition
Hinson Basket, Removable Side Case
Sparks 8 plate clutch
Custom graphics and seat cover
Custom air intake with K&n Filter
everything is polished and billet
Roll Design chrome swing arm
Elka dual rate ssd with LT linkage
TCS ZPS, douglas ultimate billet beadlock wheels with Maxxis Razr's
Roll +1.5" chrome anti vibe stem with Tag T-2 oversized bars cr hi bend
Herrmann arms Trail Tech HID Lights w/ custom billet mount (for the dunes)
Overized UM vented oil tank FST oil cooler kit and even more