98 hx problems, but whats new

[lottaspott]

i am driving a 98 hx 5 speed that i bought brand new back in high school. Back then i could get any info on mods and absolutely no parts for the hx. so i just made due with what i had. it has had a ex header on it since 99 but because of the manifold cat combo i left out the pre cat o2 sensor and i have had the CEL on ever since. i had no emisions laws in south carolina so i never really worried about it.

now to present day, it ran fine for a long time but now it has begun to run really rich and smokes like a freight train above 3000 rpms. i am about to atempt the swap over to the ex head and ecu, will anything else be needed for the swap and how hard is it. also, what needs to be done with the exhaust and the hx wiring for the o2 sensors to get it back to running like a normal car, but with a little more power.