u unplug the tb whilst the battery is on then it will bring up a p1612 code but it will be stored and not active
u unplug battery then u have to get through stupid amounts of petrol whilst the ecu is relearning
gasket is on the inlet manifold and rarely u need to replace
oil residue is just the engine breathing, it if is seeping on the outside of the throttle body then it is breathing quite heavily and usually on the 1.8 & 2.0 ecotecs did it as standard
