I have a 2003 Fatboy with a Vance and Hine's 2-1 exhaust. I took it by a mechanic because the plugs were white and he told me that I am missing some kind of tuner/module that goes under the seat. He said if I do not get this part I will mess my valves up. So I can either buy this part or put factory pipes back on.

Does this sound accurate? If so, what is the exact name of this part I am missing and how much does it cost?

 

mmmm do you have a High-flow Air Intake? If yes then you will need one of those "under the seat thingies" something like a power commander or SERT or others like that.

Is your bike Carb? Not sure exactly how it works with Carbs, but EFI if you have high air flow A/C and exhaust you need to get one of those tuners to set the mixture right. Well you can also have the stealer do a one time download. It all depends on what your plans are for the bike and such.

 

It would be nice if U at least said more about Ur bike.. EFI or CARBed
a carb only needs rejetted for that change,
How many miles on her?
Do a search on plugs and see for urself what they look like and how to check them.
U can buy several type of F/M system, ranging from $150 to $1k for tuners. The more u spend the better tuner u'll get.
Cheaper one just add more fuel, where the $$$ one make changes to the whole range of timing-fuel ratio's at all rpm's. and thats where top performance and mileage comes from.
Again just do a search and read up on the subject. then U'll learn more...

 

heres just a few of the F/M systems U can get, U need to read through them to learn a little more for Ur self....

http://www.nightrider.com/biketech/m...i_upgrades.htm
http://www.alljet.com/cobrausa_harle...nt_Fi2000R.htm
https://www.hdforums.com/forum/softa...nt-needed.html
https://www.hdforums.com/forum/softa...nt-needed.html
http://reviews.ebay.com/THUNDERMAX-F...00000007261426

 

With a 2003 there are no 02 sensor plugs so the niterider system is out. Get a power commander or sert. I can get you one if you need. The above answers are correct and I assume you have an efi system according to what you mechanic said. A pwoer commander is around $320 or so. PM or email me for more info. I will be here all day to answer questions.

Drew