This is true for both the new TL and Accord V6.

Does this mean that it will not be possible for aftermarket headers to be added to these cars?

Car&Driver says the additional 10HP for the new TL comes from "bumping the compression ratio from 10.5:1 to 11.0:1, improving airflow and opening up the exhaust". Then it goes on to mention that the integrated headers help to expel gas and reduce emmissions.

That seems like an awful lot of work for 10hp. Do you think these babies are underrated?

Hell, for about 100$ a car they could have just slapped a version of Comptech's header on and been at 300hp.

 

Comptech is actually developing a downpipe for the new AV6. It's the J-pipe after the exhaust manifold. The exhaust manifold is integrated so no modification possible there.

 

What the... why would any manufacturer do that? Are they TRYING to kill aftermarket support for their cars? Bah.

Lemme integrate my foot in their rear.

 

Unfortunately, overall the aftermarket is of little concern to them. By integrating the exhaust manifold will reduce costs. Also, it allows them to locate the catalytic converter closer to the exhaust ports which subsequently allows for quicker light off thus reducing cold start emission.