woot! Another kitted chappy.
I highly doubt that four petal is just going to sit right in there without some modifications. I am using one of those $30 Top ones up on treatland right now (got the whole intake, just using the reed block), but I had to slightly dremmel open the intake on the cylinder (mainly square out the corners and widen the sides just a tad) and open the holes on the reed block to fit the bolt pattern. I tried setting in my gila reed block (same size as malossi) and it wasn't really very close).
I'm just premixing on mine now, with a 21mm carb (cable choke and malossi e12 air filter) and the gianelli pipe. Mine does a comfortable 45 and gets there reasonably quick despite my super fat jetting. The Ninja pipe has a huge restrictor that basically part of the header and really not very easy to remove unless you chop the header and weld on the one from your stock header. Other than that, the chamber is super nice and would likely rev out much higher than the gianelli (like a foot of header pipe).
I can't imagine what these bikes would do if they didn't weigh a ton. Luckily the bottom end is rock solid, so I guess there are trade-offs.