I just finished making and installing a 2 inch ID slash-cut straight pipe that slips over the head pipe and bolts to the rear mount and the two-bolt tab under the engine.
It seems to have about double the performance that it had with the muffler (or maybe it's an illusion that comes with the extra-loud music...)
The backfiring is now loud enough to be mistaken for gunfire! I'm also noticing that when I park it after a ride, there is a very hot smell.
Has all this free-er breathing and increased performance put me on the edge of burning something up? Is it possible to be too lean even if running good?

The problem with a straight pipe, besides the completely unnecessary and obnoxious noise, is that it usually does not help performance. It is a resonant system. The exhaust pressure pulse travels to the open end and reflects back as a negative pulse. If the timing is right, this negative pulse arrives back at the exhaust valve during the valve overlap, when both valves are open, and causes the intake flow to begin more quickly. But this only happens correctly at one engine speed. At other speeds the pulses can interfere in such ways as to decrease performance. The slash cut "broadens" the pulse just slightly, and the "step" between header pipe diameter and exit pipe diameter introduces another set of pulses to confuse the issue. Longer pipes cause the resonant reinforcement to happen at lower rpm; shorter pipes work better at higher rpm. Pipe diameter is also important. Wider pipes make the pulse sharper while narrow pipes broaden it. The pressure pulse travels through the pipe at approximately the speed of sound, which varies with temperature of the exhaust gases (usually estimated as 1600 fps). Bluntly put, you have probably reduced your bike's performance instead of helping it, and you have made your bike - and yourself - more obnoxious to your neighbors.

Thanks for the pictures. Those reflections make it difficult to tune an engine with straight pipes, because at some engine speeds they help the engine to breathe, while at others they hinder breathing. Carburetor jets are fixed, so the mixture that is right when the engine is "on the pipe" is wrong at other speeds. It is actually possible, if the planets align just right, to have air blow back out through the carburetor, then be re-inhaled. On each pass the carburetor mixes more fuel, so the mixture can go horribly rich at certain speeds. These effects help explain the "dip" at mid-speeds on some torque curves.

Aftermarket exhaust makers usually promise increases in horsepower. But they don't mention the rest of the story. Horsepower is the product of torque and speed. To increase horsepower one or both must be increased. Speed usually cannot be increased very much without shortening engine life, so torque is left. The problem is that torque cannot usually be increased over the whole torque curve. Think of the torque curve as being made of a piece of string. If you pull it up at one speed, it goes down at another. Aftermarket pipes usually manage to increase the torque just a bit at the top end, where they can advertise horsepower, but the decrease at the other end usually tends to make the engine less "driveable." Same thing happens with "race" cams, but that is another subject.

Lots of good theory here...I too run a straight pipe,and it is less "obnoxious" than any of the Harleys in my neighborhood. I rejetted and opened up the filtration system to match. Mine is a short straight-cut though. About 9 inches linger than the header.

My main reason for going to an open exhaust was to be noticed in traffic.

The good news is that it seems to work and I'm being cut off less. My bike seems to run better, accelerate quicker, and I have picked up 3-5 mph onthe top speed. Mainly I like it better since it doesn't sound like a sewing machine anymore.

Obnoxious? Meh. People who don't like bikes don't like bikes. I feel mine is safer now so tough luck to them.