not sure how much different sedans are from hatchbacks and coupes but it sounds like the swap makes it sit lower thus the header is banging everything in site...could be the car is too low...a friend of mine had an ls/vtec four door teg ls...and his shit was slammed with rsr springs...damaged his dc sport headers...so i dont know if it will be swap related or lowering....i think im gonna go with the lowering issue cuz the block is the stock block and would scrape the header regardless of motor...raise it a bit...by the way he damaged two pistons due to the header damage....compression on 2 and 4 was alot lower...we took off the headers and voila...dented up to hell...good luck and keep us posted on ur ride....