I'm running a Dynojet Wideband commander
http://www.widebandcommander.com/
Their are plenty others out there that all work well as long as they are wideband technology. I like this particular one because of the analog guage instead of a digital readout like many others. It came off my wifes car, for the money I would not have gone out and bought any Air fuel monitor system system but since my wife had already bought it for her car when she traded the car I stripped a lot of aftermarket stuff from it and this ended up on my bike.
The bung on mine is welded on the exhaust pipe about 10" before it enters the muffler on my UFO's.
It's oriented facing inward towards where the center stand would be if there was one.
At the point it's mounted it's reading the front left and right rear cylinders. It is not monitoring the other two cylinders. Ideally you do want to monitor as many as possible, but monitoring one bank of a V motor is pretty typical in the forced induction world.
Typically O2 sensors need to be about 30" or less from the exhaust port.
When I had it on my stock exhaust I just had it reading the big main "box" before the mufflers so it WAS reading all 4 cylinders back then.
You said "crossover" but since you also said HMF I think you may be refering to one of the rear cylinder down pipes where it curves around underneath the tranny and into the exhaust tube coming from the front of the motor.
You do not want to put it there as it will be reading only one cylinder.
If you DID have a crossover I wouldn't put it there anyway. The exhaust velocities are lower thru a crossover which can cause an air feul monitor to be sluggish.
HMF's and UFO's don't have a crossover, they are just basically two individual "two into one" systems. At least all the ones I've seen are.
Marks exhausts" are very simiar but they do have a crossover that runs directly back and forth between the exhaust pipes shortly before they enter the muffler.
I also wouldn't waste you money on one unless you go with some type of wideband technology. Narrowband o2 sensors simply read above 14.7 or below 14.7 and are not capable of saying how far away from that number they are. The MFGR's put all kinds of pretty lights and stuff like that on them to make you think they are giving more info but they are not.
Hope this helps,
Rusty
