We just totally rebuilt our L67 with the addition of a mild cam and headers. I'm showing a random misfire code which I know is the result of the cam. I'm going to get the car tuned in a week or so and have that code removed. The car is running great so far after about 400 easy miles. The problem I have had since the first start on the new motor is that the cooling fans won't come on unless you turn on the AC. My friend changed the PCM to have low speed fans come on at 186 and high speed at 190. The inside gauge is showing 210 and the fans don't come on. I turn the AC on and the fan comes on and the motor cools down. I replaced the coolant temp sensor with the build and thought maybe it was bad. I just replaced it with a new AC Delco one and am having the same issue.... The guy at AutoZone mentioned it may be a relay. Any similar experience with anybody? Thanks for experienced advise