The TSX here has a few upgrades already but one thing holding it back is the tiny header with little primarys and 2.25" collector.It then goes into a 2.25" cat which does help either.
We built a 4-1 header, with stepped primarys, eaqual to within 1" going into a merge collectors with a 2 3/8" throat then to 2.5" exit.
Here's some pics


Due to the mass produced headers on the market you don't see many hand crafted headers to this quality these. Most people building headers focus more on making it looks shiney and fit in a box to ship to someone across the country.
There's very little caculating involved, this is more important than the rest of the exhaust system,.



Plenty of ground clearance


Here's the before and after

LHT Has built headers for many vehicle in the past, we can custom build to any seup.





The header is going to be ceramic coated black to keep the under hood temps down. The factory installs a heat shiel for this purpose.

More to come on this car.