I have a 2008 HD FLH with a pair of Screaming Eagle slip on mufflers and I just bought the matching Screaming Eagle AC upgrade. Will it be ok if I install this breather kit without flashing the ECM or installing a Fuel Pack? I don't want to hurt my engine. What Do you think? Thanks in advance for any advice you can give.
Our Answer
Dougster....thanks for the question, this is one we get a LOT and unfortunately you won't like the answer. Harley Davidson motorcycles are set up from the factory to run extremely lean and to be honest, they are right on the ragged edge of trouble right from the factory. If you add any modifications that allow the engine to breathe even better, then you are only exacerbating the problem.
The good news is that you don't have to pay the dealer to flash your ECM if you don't want to. My recommendation would be to pick up one of the aftermarket add-on fuelers that you can buy. Several great examples are available including the Dynojet PCIII or the Cobra Fuel Pack as two examples.
These boxes will basically intercept the signals from your O2 sensors and increase the time that your injectors stay open in order to richen the fuel mixture. This will reduce your cylinder temperature dramatically and make your machine run better than ever. Harley's cost money.....everything you do leads to more money.
It's a sickness. 
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Chances are really good you will need to remap the motorcycle. I wouldn’t pay the dealer to do it either though. There are a number of aftermarket kits you can do it yourself with and I would go with the PCIII. It’s simple, it works and it gives you a ton of flexibility.
If you ever modify your motorcycle a lot then you just download a new map and your bike is good to go. It’s pretty cool.
Sreaming Eagle pipes are not any different than stock harley pipes. In fact the company that made SE pipes now make Rush slip ons. Me personally I don’t think i would even bother with the AC kit. It costs too much to add.
You have 3 choices and two of them are bad.
1. You can run it without the new map and melt the engine down, oh and your warranty might be voided because you didn’t re-map the engine.
2. Install an aftermarket fuel mapping device on the motorcycle and void the warranty.
3. Do the re-map and keep the warranty running, which would be my selection.