I have an 02 coupe with Z catbacks and a Blackwing and I am thinking of installing the best headers I can get, either LG or TPIS.I also need to get the best high flow cats that will not alter emissions. I am wondering what I can realisticaly expect to gain with this setup and what the problems will be after they are installed.Will it make the system much louder? Ground clearance, leaks at flanges, heat or emissions? I remember some of these problems years ago on my Z28 and would like to avoid. Also, how hard are they to install assuming one has access to a lift? Thanks for any imput.