95 2.0L engine ticking from injectors?

[spec_77]

Hi,
I recently bought a used 95 Mazda 626 2.0L automatic with 135k. I've noticed a ticking sound genterated somewhere around the injectors whenever I have the gas pedal pressed slightly. If I increase the pressure on the gas pedal, the ticking sound goes away. Seems to be that if the engine is around 1000-2000 rpms, the ticking sound starts, then goes away at higher or lower revs. I've changed the oil and oil filter, fuel filter, and spark plugs. I've also tested the spark plug wires and injectors for resistance, according to the tests in my Haynes manual, and they were all within specifications. Any ideas as to the source of this problem? Is it anything to worry about? Thanks

-Tom