i've got xforce 4-2-1 headers with a full xforce cat back system as well for my civic vtir coupe. the whole lot is stainless steel and mendrel bent.
the top end power has greatly improved. i got it all done for $2000.
it gives almost the same amount of power as the top jap bands do (eg. apexi, blitz) but half the price.
it is well worth it.