I just installed the Vance & Hines Power Dual pipes, with Monster Oval mufflers. My ride is a 2010 Utlra limited with the 103.
I rode with a 2010 Screaming Eagle Ultra last week with the same set up. Rider advised me that on the dyno the results were poor at best. Dyno tech told him he didn't believe it was the Power Duals. He felt the Monster Ovals were to restrictive.
With this in mind, and my Dyno run set for a week from today........I noticed the Monster Ovals had a cap about 5-6 inches from the rear. You can't see down the center of the muffler like most other products. Question: If I drill this cap out, will it increase my flow and give me a better dyno run? Anyone do this or hear of it? Any imput would be appreciated.

yo bluedot..

the whole system must run together as they are all connected and dependent on one another as in the air intake....the fuel intake...the exhaust....are all interconnected and by changing one you may be forced to change another or the change you make can force a change to another without that intent. harley has over a hundred years fine tuning these engines.....and we have over a hundred years been doing our own fine tuning with some good and some not so good results.....is your intent to produce more power or change the sound or both.....would hate to see you punch holes for power and then hate the new sound....
please keep us posted on the mods you make and the results you get as we out here are interested and always want to know what we can do for more power and sound hahahaha

The cap I was asking about is a 2 1/4" freeze plug. Took the muffler off. Removed the end cap. Placed it on a 2" x 4" and used a steel rod to drive the plug out the end. It had four spot welds. Sounds a little louder, not bad. Still not as loud as the Rineharts. I can now see from one end to the other. Should have unplugged it enough to pick up the horsepower numbers on the dyno Saturday. I'll keep ya posted.

Hi Bluedot532,
Welcome to the forum. I agree with roadkinging, You can start to do modifications and they can just get bigger and bigger. IMO knocking the plug out of the pipes will not get you any more HP. It may run a little better and sound louder but I think that is all you will get with that mod. Take you time and ride it, see how you like it and how it rides. You may like it just the way it is.

Ride safe and enjoy.

Big Lenny

OK, Dyno results:
2010 HD Ultra Limited, 103, with Arlen Ness air cleaner, Vance & Hines Dual Power pipes with Monster Oval mufflers (freeze plugs knocked out), HD race tuner.
78.09 HP, 93.52 TQ.

ok bluedot532

thanks for the update .....wish you would have supplied the test results of before and after the modifications and included the fuel mileage per/gal of both before and after and the sound change from the tailpipe.... .. not sure but i think you sound happy with the results you got so i offer you a congratulations . the only one you have to please is yourself but we all want to be happy for you....and we do want to know if you archived the results you were trying for...thanks for the update...what color is that bike?

Roadking. I didn't get MPG because the bike is new (2 months), 2200 miles. Start dyno was 76.27 HP and 89.51 TQ. The Monster Ovals with the plug knocked out sound great. Low and throaty. Still much more mello that the Rineharts. I'll start tracking MPG on my next road trip.

Roadking.....senior moment. Bike is Black over Black Ice.

hey bluedot532

???? why no pics in your gallery??? you know the rules about not sharing. hahaha waiting.

not sure if this helps, but I found a exhaust comparison breakdown on another forum site called hdtalking. it was a really comprehensive breakdown for those with questions about custom exhaust. May be worth checking out becuause it explains why certain pipes, slip-ons etc help/hinder performance.