Hello! I'm having trouble with my 92 volvo 940 GL. It won't pass emissions, the NOX ppm reading is too high. It is at 1600 and needs to be no more than 800. I have a new cat converter on, and i dont know what the issue may be. I know nothing about cars, let alone volvos and i need this car on the road so i can start my new job. I've googled why the NOx readings might be to high, and was told by Midas that it might have an over advanced ignition timing, bad egr valve, or bad 02 sensor. Please help!