There are detailed write ups from Kevin Landers at Rotary Resurrection.
Look here for S4 emissions removal
http://rotaryresurrection.com/2ndgen...s_removal.html
or
Look here for S5 emissions removal
http://rotaryresurrection.com/2ndgen...s_removal.html
BTW he has some nice write ups on other things under his Tech section check them out.
http://rotaryresurrection.com/2ndgen/techmenu.html