Start with the fuel rail - it's a common RENIX problem. Change the fuel injectors, if required, and change the o-rings at both QD connectors.
If there's a leak at an injector, check carefully - especially if the injectors are still original. They can be replaced with Ford or Chevvy 5.0 units, rated for about 19#/hour. RENIX injectors (the ones with the metal/plastic crimp joint halfway up) are known for leaking after about 150Kmiles.
Those little QD fittings at each end of the fuel rail are just known for leaking - I don't know why they're used. One project I've got in mind is redesigning the fuel rail to accept either -AN or -JIC fittings - lacking o-rings and sealing metal-on-metal. I've just got some other things that need doing first...
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