You know, ever since I posted my reply above, I've been thinking about this further. It's a common topic that comes up A LOT in discussions of swapping pipes. And after more thought, I want to retract - or at least clarify - my original reply.

The short answer: I agree with todd-67. I'm assuming the OP is running with an older, football intake, since he said he only swapped exhausts. Not intakes. But even though those are well sealed, I think if you put more free flowing exhaust components on, you reduce the overall resistance to airflow in the system, and you WILL get more air flowing into the system. The counter argument says you won't, because the airflow is still limited by the OEM intake. That was my initial position and it's true - to a point. The intake will limit the maximum air into the system. But that doesn't mean there wouldn't be an increase in the SPEED of the air coming in, would it? If you remove the resistance to airflow within the exhaust, it seems safe to assume that the airflow IN the exhaust would increase, pulling air faster into the engine. So even though the intake opening is a fixed size, the SPEED of the air flowing through that opening increases. This increase in airspeed into the engine would result in more air in the engine at each combustion cycle. I don't know if this would be a significant increase in the amount of air or if it would be minor. But there would be more air in the engine on each combustion cycle.

I think one thing we all agree on is that Harley's (especially new EFI ones) run lean from the factory. So even if the exhaust change produces a minor increase in air in the combustion cycle, that means the engine will burn more lean (hotter). Whether the increase in heat is enough to be uncomfortable, noticeably affect engine performance or damage the engine, I don't know. Most people I've talked to think it's not harmful. But one gentleman above says he believes it burned out a valve. I suppose it depends on the specific bike.

For optimum performance, maximum rider comfort and to minimize any possible risk to the engine, it would be a good idea to get a tune on the engine after mods such as this. I missed the fact the OP also swapped header pipes to more free-flowing ones. If you change the entire exhaust to a free-flowing one, I'd err on the side of caution (and performance) and get a tune done (or buy a tuner). But I'm stubborn, so I'm going to hold onto the stance that swapping JUST the slip-ons doesn't necessitate the need for a tune (or a tuner), since the stock headers wouldn't allow for a significant decrease in airflow resistance through the exhaust, thus there wouldn't be a significant increase in airflow into the engine.

Thanks for indulging my lengthy reply...

 

I would go and get the V&H FuelPak 3. The bike will run cooler and be more responsive.

I paid under $300 for mine on a black friday deal last November from Leather Up. Look around - there are deals out there.

It's very easy to tune and you can auto tune and dial everything in on a few short rides.