I have a question are the primary cats on the F high flow? If not can they be replaced with 100/200 CEL racing pipes/downpipes? Are the cats welded to the cats?

 

Are the cats welded to the cats Do you mean are the primary cats welded to the exhaust manifolds? If you do, the answer is yes. And, yes, I do believe they are high flow

Lou

 

does not look high flow! lol!

 

Yea I don't think they are high flow. They are pretty restrictive.

 

The cats appear to be of high flow variety to me, why would you think otherwise? The manifolds, while certainly not headers, look pretty good, IMHO, based on the space Lexus had to work with. They appear to make an attempt at exhaust scavenging.

Lou

 

Barely an attempt. They're tying adjacent cylinders and that's just wrong from a scavenging perspective. Sure they did OK with the space allowed, but they could have done better. It seems they didn't spend their money getting the exhaust as nice as they could have - maybe that's why the power numbers took so long to be released and the specific output is significantly less than the 2GR-FSE which has the same bore and stroke with two less cylinders. I'd really hoped with the G heads we'd see even higher specific output than the 3.5 liter V-6, but I can see in these pictures Lexus cut corners here to give us an exotic valvetrain and more capable head (with the right pieces added later to make power competitive with the C63 AMG.) It's very possible this exhaust design is responsible for our class leading fuel economy.