I have a 1992 Ford F150 V8, 302 engine. There is a ticking noise in the right side of the engine compartment under the hood. I lifted the hood and cannot hear the noise, I raised the RPM and still could not hear the noise. When I get in the truck and drove down the road, sounds like a cross between a valve ticking a fuel injector or an exhaust leak. I hear the noise, it only ticks under a load. I have changed the exhaust manifold gaskets on both sides, donuts on right and left side and put a new muffler on the truck. engine seems fine, just still has the ticking noise. Any suggestions?