whoah there dude.calm down :p.ok to change the o2 sensor you will have to buy a o2 socket and remove about 1/4" of material off the end so that you can fit a ratchet in there, else its gonna hit the brake booster.yes, the o2 sensor from the 84 200sx ca18et will work, ive had it on my car for a week now and it runs fantastic.advanced timing is bad, its a recipe for disaster.you need to hook the tach up so you know what the engine is tuning out, or alternatively on the efi harness there is a connection to read the rpm, the wire is yellow and red and is often capped off with a dust boot (on of the round random things on the efi harness).i would lower the idle then adjust the timing as timing is interrelated to engine speed.trust me, with the right timing and a new o2 the car pulls harder and feels better than the timing set at 30.sil820 wrote:ive been having this same damn problem..the only thing is i dont have that many tools to do all that.. how do i change my o2 sensor? disconnect the down pipe or exhaust? so the 1984 200sx with the ca18et engine o2 sensor will fit perfect? my car has been running hella rich and the timming is horrible its all the way 2 the right, i thought advanced might b good but guess not.. right now i have no RPM readout so i dont know what my idle is at. so should i just adjust the timming back 2 normal w/o messing with the AAC valve? what should i do?