First go through I failed because of co and hc being to high, went back to mechanic and he said prob because of 180 on motor and timing is out due to slack in chain, he adjusted and my numbers did drop but now failing nox. Any legal sugg? I know plenty of illegal ones. My mech usually runs me through but his machine is down, so no bueno. And a hundo will buy me a sticker elsewhere, but whats the issue. If its been running rich this long is the cat shot? Enough to fail it this way? Timing adjustment kicked the crap out of the co and hc, and sure as hell brought some life to a tired 305.