Today I notice a slightly louder sound from the engine bay and when I check my O2 housing has 2 missing bolts (one bolt and one nut). I am not sure if it was that I did not tighten them hard enough (I used a torque wrench) or if I should use thread lock on them. Is anyone using threadlock on the hotside. Did you use red or blue compound? Hopefully I can replace the bolts without having to remove the exhaust manifold. If not that would be a real pain in the neck. Looks like at least I will need to remove the radiator. That sucks, big time.