My cousin has a 93 accord and she is having trouble passing smog. The ASM Emission test results stated that the NO (PPM) max:490 and 511 ave: 165 and 128 MEAS: 882 and 874 and both lines failed. When her dad told me about her car my first thought was to check her O2 sensor or her EGR valve. then i started to look around and that was the basic consensuses of what i thought. my next idea was to just give the car a quick tune up and change the spark plugs and wires, change the air filter, and clean the throttle housing and possibly the O2 Sensor just for safe measures. also thought maybe it needed a new CAT but not sure. i also saw that there gas cap could be lose too but its dark out right now so ill check it all tomorrow. but i just wanted to know if i should keep a look out for anything else that i didnt find or am missing. help would be GREATLY appreciated. she just got her license last week and this is her first car so id really like to help her out.