If you are in CA, the AQMD changed SMOG specifications for older vehicles a couple of years ago. My 1993 which had passed every year failed then. After spending almost $1K at the mechanic it barely passed. I told him that it was running cool because I had put in a 180 degree thermostat, but he said that did not matter (BS). I just had it smogged again after installing a 195 degree thermostat, and it passed with no problem. The SMOG technician even remarked how few emissions it generated for a big block. Bottom line, the high temp thermostat is a must to reliably pass under the revised regulations.