Get a mechanics stethoscope and pin point the exact location of the tick.

 

An air leak in the exhaust BEFORE the O2 sensor will affect the signal to the PCM. It might pay to look for any more exhaust leaks and put a new O2 sensor in.

 

The link for the tester didn't work, but it sounds like you are using the pen-like one that you hold up to the wire, and a little orange neon bulb glows inside it?

Beware that type of tester only tells you there is electrical current flowing at the location where the tester is touching the wire, not all the way to the plug. If a plug wire is grounded out someplace between the tester and the engine, or if the plug electrode is shorted, current will still flow and the tester will still flash. It's best to use that kind of tester right where the wire meets the plug boot, except of course you probably can't reach there without burning yourself.

 

That's what I did, I pulled the fuel pump relay, then had someone crank it while i put the probe where the plug actually connects to the wire on the wire, one was weak, which I replaced that wire, the other 7 lit up nice and bright.