I have a 1987 240GL Sedan that is in good shape with 179K miles on it. It just failed the New York State Emissions test with a high NOx reading. The mechanic informs me that I need a new catalytic converter. I am not sure that this is true. I installed a Walker replacement cat 3 years and 30K miles ago. The car has passed emissions on previous years and runs fine. I noticed after I got the car back from the mechanic that hose from the air cleaner to the exhaust manifold was hooked up. I have kept it disconnected. I don't like to do anything that is different than Volvo inteded, however, after replacing the thermostatic valve in the air cleaner and still getting stumbling on medium warm days after stopped at a traffic light, I disconnected it. The question is; can the engine sucking in warm or hot air effect the emissions and will it cause the NOx to be high?