I heard a tale that if you remove the plastic back from the 07 Sportsters, you can pick up a slight HP raise. It is only there for emissions.
Does anyone know if that is true?

 

Some guys have cut the plastic (backplate) to allow more airflow. I think I've seen some pictures posted on this. You can't totally remove the backplate, part of it is needed to mount the air cleaner. At least that's the case with the carborated bikes, I'm not sure how the 07 air cleaners mount. By cutting out the backplate it allows more air to flow and can increase the HP. I'm not sure how much increase in HP you would get just from increasing the air going into the combustion area of the motor. This can also be accomplished by installing a Screamin Eagle Air Cleaner, or some other similar aftermarket air cleaner system.

If you also install some more free flowing (louder) pipes, that will increase the HP. However, you will have to get the dealer, or someone, to download the remap for the Fuel Injection System. This procedure, of opening up the air input, air output and remapping the Fuel Injection (or rejetting the carb), is commonly referred to as Stage 1 conversion.

Since it is pretty much a reversal of governmental emmissionsmandates, it's also referred to as "The Harley Tax".