on an 01 RS...hmm....there is a vacuum hose to the pressure regulator and cruise control on the passenger side pointing towards the rear. there is the brake booster on the driver side, also pointing to the rear. you can also try looking at the manifold gaskets for the intake, TB, MAP....ummm. IACV too. maybe check the bolt tightness on some things. also check the hose for the gas tank pressure relief, it's right behind the alternator/PS pump. may have a purple electrical connector.