Engine knock/rattle vs. fuel injectors??? Any help?, Video and description... Options

[celicakitten]

So I've had my car for three months now and still cannot figure out what this noise is! I'm by no means a mechanic but have common sense around cars, celicas inparticular. It's a mostly stock 7a-fe with 194k and 5 spd tranny. The car runs fine, and since I've had her changed the oil, spark plugs/wires, exhaust manifold/down pipe(original was cracked), and have had no other problems...not even a check engine light. I can't find anything loose that would rattle, but there is a significant power steering fluid leak.

http://youtu.be/FOrH0HC7l5w

Please see the video I put on youtube to hear the noise, which is most notable on a cold start and anytime I'm constantly holding revs over 2500rpms, but will stop if I floor the gas or let off it completely...It's very annoying on the freeway(but isn't noticable with the radio on! ha!). I'm thinking maybe a bad piston ring, or possibly something in the fuel injectors??? I should also say the noise does seem to emit from the passanger side of the engine bay. I'm worried it may be time for a rebuild as I do not know how the previous owners treated her. If that is the case my biggest challenge would be finding someone I trust to do the work, but I'm sure you guys can help point me in the right direction for that!