My car makes loud ticking / clacking / knocking noise
when under load. It appears to be coming from the top
of the area between cylinder 2 and 3, near intake manifold.
Once the car is up to cruising speed, noise dissipates completely
but returns when the speed drops and has to be built up again.
Car appears under stress and underpowered while stressed,
but runs fine and gets good mileage once it gets going down
the highway. Since the noise is not constant, I'm eliminating
severe damage to the engine, cylinder head, or valve train.
Any ideas ?