/// Warning Keith--- The 0-rings in the injector holders are high temp. Use only Volvo parts or insist on the high temp 0-rings inside the holder. These should cost $1+ each not 35 cents. If you use the regular 0-rings they will shrink, harden and be almost impossible to get out withour breaking the holder. There is a thinner 0-ring on the outside of the holder and it can be either type since it can be cut off. The advise on the intake manifold gasket is good, try spraying carb cleaner around the gasket and see if the idle clears up. Poor idle is usually unregulated air. --Replace the 0-rings first.