The car only has a bit over 100k? Unless it's leaking, I wouldn't touch the pump.

 

I would first try an oil change.

 

Also a 1/4 to a 1/2 quart of ATF in the oil will help free up and pump up the lifters. Do this about 500 miles before an oil change.

 

Really, TOD is VERY common for these cars. Don't let GD scare you either. There is no need to tear down the motor or spend $1000 right now. People have driven subarus for years with this ticking. It' not a very big deal. It can however make the motor lack power and have poor response, so fixing it may help you're problem.

 

I'd add 1/2 quart of Dex/Merc ATF to the oil and run it like that for a few weeks. Then change the oil. I'll bet within a few days the ticking will have stopped.

 

If getting rid of the ticking does not improve power, then I would suggest that the timing belt was installed wrong, a tooth or two off.

+1 on the normal Low reading on oil pressure gauge.. For peace of mind I usually ignore my idle oil pressure because I dont like seeing "0", even though I know it's not... I look at the gauge at over 2000 rpm, and 45psi makes me much happier.

 

+1 on trying ATF in your engine oil, it is a detergent and may help clean up the oil passages/gunk/residue in the lifters themselves.. I guarantee, with over 100k miles the lifters are gunked up on the inside. As G said, not too much though..

 

+1 on the "mickey mouse" oring thought.. Every single one I've seen has been sucked in, this will lead to aeration of the oil.. being the Dr. Ft is the last lifter to get oil, it sometimes doesnt get enough to pump up. I've noticed the most common reason for these Orings to suck in is due to high rpm of the engine..You mention it just started after a couple 6000 RPM pulls.. Sounds like this could be the issue. I've sucked 2, even after gluing and silicone the stupid things into the groove and everything, but I regularly turn 7000+ rpm.. I advise against this. (do as I say, not as I do type of thing... lol)

 

IF this noise persists after cleaning w/ATF treatment, it may be time to delve into the front of the engine.. +1 on the oil pump being WAY easier(less labor intensive) than the cam carriers, specially in the car. My advice would be to have one of your closer members, who's willing of course, come down and listen first of all.. then maybe help you repair it.. Just about anyone can work on one of these things, with the proper instruction.