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Where will you be testing? At termination or at furnace with flue disconnected?
Since the 58MCB is a high efficiency condensing furnace, the flue temp should be approx. same as return air temp and never exceed 125 degrees. This is why the PVC is allowable as vent material.
The carbon monoxide level should be below 100ppm with flue open and never above 400 with vent blocked for testing.
These levels are with sensor inside the pvc pipe