By Jay at SuperDrift "Well, there has been many speculations and researches by shops, but we got this "unofficial" explanation straight from the horse's mouth. We can't name who, but he/she worked on the Gen coupe project. The rev hang (partial opening of the throttle) was put into the throttle body control in order to lessen the blow by gas emission. During the development Hyundai researchers experienced that if a throttle body closes immediately, pressure inside the engine(crankcase) becomes so great, it caused more oil vaporization than usual. This is quite normal for any turbo charged engines, but Hyundai wanted even better emissions and didn't want to deal with the "oil loss" issues. Thus by partially keeping the throttle body open even after gas pedal has been completely released, pressure can escape from engine. So, here is what we found out. Solution to the rev hang issue will be to fix the throttle body control codes in the ECU, install oil catch can and add oil every month.."