Tooter manifold / Corolla TB / DC Header / etc....

[Jason@SportsCar]

You would be surprised at how a thermostat can put a car out of whack... This past weekend I helped my neighbor install a thermostat in his work van. It failed emissions, when he got the ECU scanned by a GM tech it was stuck in open loop mode, and would not get above 150f - which is about the temp of that unit you put it. In his case when he had the radiator replaced a few months back some knuckle head cut the core out of the thermostat (no idea why, could have been stuck), we put a new stock one in and now it passes smog.

I run a cooler unit, because we run a 30-40 min race and spin over 7000rpm, but I have complete control of my fuel via my AEM ecu.

On a road going car with a stock ECU you have done nothing but fatten up the mixture. No upside.