94 Z28 Emissions

My emission results for 94 Z28. Any recommendations would be appreciated.
Engine has 215k. Has edelbrock headers, slp exhaust from a 97 Camaro (2 cats). Just changed optispark/water pump. Hypertech has been used.

ASM2525 Test
Limit / Reading
HC 55 122 Fail
CO% 0.31 1.57 Fail
NO 408 756 Fail
RPM 1875
Dilution 14.9

Curb Idle
Limit / Reading
HC 200 175 Pass
CO% 1.00 3.15 Fail
NO N/A N/A
RPM 808
Dilution 15.3

The fact that HC, CO and NOx are all high under load would seem to indicate a problem with the cat. High HC and CO might mean its running rich, but the NOx would be low in that case. High NOx can indicate a high combustion chamber temp, or running lean. But with high HC and CO that doesn't seem to be the case.

The fact that HC, CO and NOx are all high under load would seem to indicate a problem with the cat. High HC and CO might mean its running rich, but the NOx would be low in that case. High NOx can indicate a high combustion chamber temp, or running lean. But with high HC and CO that doesn't seem to be the case.


Thx for the reply.
Why would the HC pass during the Idle test while still failing the CO?