hey scotty i have a 3.5 02 maxima i just bought and i could not have bought a better running or clean car there was absolutley nothing wrong at all with the car but i put 20000 miles on it and changed the oil and oil filter then i decided i wanted to change the spark plugs cause i dont know when the last time they were changed i had to take the manofold off to get to the back 3 plugs i put the name brand 'bosh" spark plugs into the car and it was running very bad. so i went and bought the plugs like i took out and they were ngk, now i have it running ok but nothing like it was and ive replaced all gaskits two times, i have a bosh obd 1 and 2 i keep it pluged into the car im getting the coad p0430 all the time and when i dog it out i get a bank 2 crank sencer. ive tested crank sencer its good and gettin power dont know how to test the cat.. or o2 senser oh and while i had the manofold off i cleaned the throtle body and was getting a ilde air code i performed a ilde realearn dont know if it worked or not but no code when the car is running anytime i rev up the moter or just let off the gas to stop the rpm needle falls to 1000 then revs up to 1900 then back to idel normal

No. 1-1

that's the inefficent cat code, those things eat up cats. odds are you need a new on, have a pro test it with his special equipment, they are complex but do go bad a lot on that model