260s run well on hot engines, as compared to many other models. It is more particularly sensitive to any imbalances in the engine management, i.e. CO level adjustment, plugs, oil, etc ... that may have a bearing on others.
Is there anyway of going through the checklist on your brochure and take the car out for a test run before going in for the test proper? Surely some workshops around your area may have the instruments ready?
Singapore has an equally stringent test for older vehicles and I used to reduce the CO mixture in my brother's 123 200 just to pass the emission test. And then re-tune the levels for optimum performance.
126 tailed by a 203, 129 leading the pack.