Engine temp has little impact on exhaust gas temp. That is affected by engine tuning conditions and also means not just ignition timing. Make sure you have the right heat range spark plugs in it. Also make sure your leads and coil packs are nice and healthy. Good spark = cleaner burn. Now something a little stupid. If your combustion chambers are fouled up do not use a fuel additive. It will ramp your emissions especially this close to a smog test. You could run E10 for the test only as it produces lower emissions. Do an engine oil flush and change. The crap in the crankcase can impact emissions results as well so purging the contaminants out of the sump and block will help.