Bubbie,
Based on the information provided on this site I made the following changes to my Ultra Classic (from original stock) and I am very happy with the results and I have had no issues with 4 months of use (100 miles/day commute to work)
Screamin Eagle air cleaner/intake
TFI (Dobeck Performance)
Vance and Hines Slip-on Ovals
I did all the installation myself and after some slight adjustment to the TFI (mainly based on trading some power for better fuel milage) and taking a peak at the spark plug color from time to time, I am very happy. In the stock configuration my plugs definitely had a "straw-like" color. Now, they are what the typical photo of "normal" is supposd to be. Since I made all of the changes at one time, I can't say how much impact each individual change made. The mufflers were a tough call for me because sound and loudness is a very personal experince. I ride with a full face helmet and earplugs on my daily commute even when I had the stock mufflers. But, I can still hear the stereo (although muted, I would not describe the music as simply a "background noise" ) over the mufflers/helmet/plugs. I would suggsest that the mufflers (ovals) are fairly mild if you stay out of the throttle or you are crusing in top gear. When you roll-on, you will definitely notice.
Of all of it the most physically demanding portion was removing the left side, stock muffler. For some reason that really siezed onto the pipe.
The Dobeck staff was great to talk to on the phone and installtion was very easy. The hardest part there was raising the fuel tank due to the fule cross over line but it was still relatively easy. I am not trying to sell the TFI unit, but simply stating my choice. I wanted something relatively simple and the idea of using a screw driver for adjustment seemed more within my capabilities and a computer program.
Hope this helps.