Wow! Just read thru the last 3-4 pages of this thread.
Yes, we've documented, on a dyno, changes in performance between many different headers, headers with and without cats, and many different slip-ons.
There is very little difference in performance, regardless of the header, cat or no cat, and which slip-on muffler used.
The three exceptions are:
1. Some low end torque drop when using True Dual headers...those are headers where there is no crossover between the front and rear cylinder head pipes. Not to be confused with Power Duals.
2. SuperTrapp, or Series E disc type Slip-on mufflers. These can add 5% or more in power, which is significant.
3. Most any slip-on muffler that a Thunder Torque Insert™ has been used with it. These can add 5% or more in power, which again, is significant.
Other areas where the Differences in exhaust can be Significant-
1. Removal of the cat will reduce felt heat to rider and passenger
2. There are huge variances in what sounds good to each persons ear. What is too loud to one person is not loud enough for another.
For those that do not like loud, a performance exhaust is pretty much limited the the disc type muffler. They are relatively quiet, but even they are too loud for some.
The best performance muffler is an open one (no baffles), with
Thunder Torque Inserts™. These are loud, and they also deliver the best increase in power. 6-10% is typical.
A compromise is an
aftermarket muffler, like the
Hi Roller or a V&H with the baffles still in, combined with a TTI. These will deliver a 3-5% increase, which is significant, definitely enough that most will feel it. They are louder than stock, but many do not find them too loud.
There are many myths regarding Harley Exhaust. Some are addressed in this
REPORT LINK, also addressed is help on picking an exhaust you will be happy with with. ie. buying your last exhaust the first time, instead of spending money on multiple systems.
For a Trike, if one is looking for performance improvements, exhaust changes will help, but in a relatively small way, and when compared to cost, they are one of the least in terms of bang for the buck, unless one likes a Loud exhaust note.
Much better performance gains can be had in other areas. There is a Report
HERE on Long Ignored/Little Known Performance Mods.
A Performance gain of 20% is not unusual when using the strategies listed in the above Report.
Kevin