HO 8.0 ppm limit 83.0/CO 0.02% limit 0.46/ NO 275.1 ppm limit 630.0/ CO2 15.01% tested 6 10 2013 Ohio E check this was a tailpipe test because the guys at the E Check were nervous because my engine was modified I passed with flying colors car had Performance Auto Werks high flow cat -Solo header-Magnaflow exhaust - new plugs -GM CAI w/ new filter -fresh oil & filter - 93 octane and was up to normal operating temperature .Hope this helps