Hello from Rockwall Texas
Other than tearing the engine down, the only other way to determine if other engine mods were done is documentation. A previous owner or dealer can help with that.
You state that you have a heavy breather and V&H pipes. Do you have a fuel management device as well to complete the Stage I ? If not, was the ECM flashed with a new map? The tuner (fuel management device) will optimize the air-fuel (A/F) ratio. Harleys come from the factory running very lean. This makes for a hotter burning engine. The SE heavy breather is allowing more air in which will make the bike run even leaner. The tuner enriches the A/F mixture helping to cool the engine and improve engine performance. The downside would be lower mpg because you are burning more fuel.
As far as power goes, it depends on the pipes you have. True duals will generally worsen power a small amount while a 2-1 exhaust may improve it. At most, you would expect about a 10% boost in power from a true Stage I upgrade.
Here is a link to the specs on your 2003 Harley Fatboy. It reports a torque of 77.4 ft.lbs @ 3000 rpm which calculates to 44.2 horsepower.
Again, welcome and ride safe.
Boog
I have an 88 engine also in my 2005 Heritage. It also had a Stage 1 kit installed on it (sounds a lot like your setup), and for this old guy (66 years old), it gets me where I want to go with ease. I can't help you with the technical questions, but I can say that I'm sure you will enjoy your new ride. PICS?




