Ok, the con is the price, yeah, we all know it.
But since I already paid for it, I thought I would list the pros, if nothing else to make myself feel better.
What it is:
1) SE intake mod, lets more air in.
2) Screamin Eagle 2 into 1 Nightstick pipes.
3) ECU flash (level 1), this is a remap to take advantage of the better air flow. Without it the engine will run too lean, and can void the warranty and reduce engine life.
What it gives:
- 18% more torque in the middle range, only 1 more hp, torque falls back to normal at the high end, near HP peak. But torque in the commonly used band is +18%, that's almost a Street Rod, which has about 20% more across the entire RPM range.
- higher mpg, about 5 mpg reported.
- factory warranty intact.
- Louder, as loud as possible but still street legal AFAIK
Let's talk about the sound, one of the big draws of any Harley.
- I have always ridden a street-legal bike, and this is the loudest one I have owned, although my BMW GS650 came close, but it sounded like a big lawn mower (single), whereas this one sounds way better (big twin).
- at idle it has a nice deep sound like a bigger Harley.
- at higher RPM's it clamps down, meaning it doesn't get significantly louder, but it's still loud, just not hugely so like an aftermarket pipe.
It doesn't sound like a big Harley at higher RPM's though, just a loud engine at higher RPM's.
- If you gun it at mid-RPM's it still has the crackly sound of what a Harley should sound like, but only under heavy throttle.
- I haven't tested throttle blips, but I think the hybrid sound is what you will get after it revs up.
- the sound exits sideways, not backwards, this is a big plus, and I think it is a stroke of genius. The air exits sideways through a series of concentric rings at the back of the pipe, there is no rear-facing hole. This is a big plus at low speeds -think lane splitting - so traffic beside you or in front of you gets more sound than a rearward facing pipe gives.
- The genius is since the sound is dispersed omnidirectionally rather than rearwards, it makes it possible to produce more overall sound and remain street legal. The law gives a db limit at 3', and having a rearward facing hotspot severely limits how much sound it can throw forwards where you really want it in traffic.
- to give you a feel for how loud it is, with fully inserted foam earplugs (33db), I can barely hear my aftermarket (but still legal) Yoshimura R77 pipes on my Honda. And it was a big upgrade, louder than the whisper quiet stock pipes. Cars hear me noticably better when I am lane splitting below 30 mph. The Honda is loud enough I would not want to ride without plugs. But the Street 750 SE powers right through those earplugs, not enough to cause noise exposure worries, but I can hear the engine quite well.
In short, the level 1 upgrade gets better and dramatically louder sound, but not all the way to a big Harley sound, or the crushing volume of aftermarket pipes, and the sound is best at low to mid RPMs.
So in summary, if you want something Street Legal, meaning louder, but maybe not loud enough to have people chasing after you because of your obnoxiously loud bike, better engine performance, and a significantly lighter wallet, the SE level 1 mod is for you. :-)
Edit: forgot you can add diffuser disks (as pointed out below), here is the link to the SuperTrapp diffuser disk kit: