Valve Chatter or knocking?

ok i have a 1999 civic dx with a nearly stock d16y7 engine (has intake and exhuast and Castrol syntec 5w-30 synthetic oil). Under full throttle at about 2.3K-ish rpms i hear a rattle coming from the engine. It sounds like a metalic tinkling and can get somewhat loud, especially if im listening with the windows down. At first i thought that perhaps an exhaust pipe was rattling against the underside of the car somewhere, but i checked and both the intake and exhaust are pretty much rattle-proof.
I was wondering if perhaps it was valve chatter (although my valves were adjusted only 15k miles ago). Im also running regular gas (87 octane). Ill try premium next tank, but is knocking plausible? Or could something cause my valves to go out of adjustment? or could it be something else?

I would try the premium as a quick test. My last 2 Corollas both needed 93 in warm weather to stop them from spiking.

wow. so i put in some premium gas and now it sounds like it should. no ticking / rattling sound!! jeez if a civic cant run regular, what car can? haha

ok i have a 1999 civic dx with a nearly stock d16y7 engine (has intake and exhuast and Castrol syntec 5w-30 synthetic oil). Under full throttle at about 2.3K-ish rpms i hear a rattle coming from the engine. It sounds like a metalic tinkling and can get somewhat loud, especially if im listening with the windows down. At first i thought that perhaps an exhaust pipe was rattling against the underside of the car somewhere, but i checked and both the intake and exhaust are pretty much rattle-proof.
I was wondering if perhaps it was valve chatter (although my valves were adjusted only 15k miles ago). Im also running regular gas (87 octane). Ill try premium next tank, but is knocking plausible? Or could something cause my valves to go out of adjustment? or could it be something else?Loose or corroded exhaust heat shields are a common problem. Mine would almost buzz/ rattle but only under certian running temp and/or load. When the car is hot try taking a rubber hammer and lightly beat on the exhuast. Other than that it could be many things from a serious engine problem to a bad pully on an alternator or AC compressor.

ahhh i fail! turns out the premium didnt solve anything.... some days its just worse than others.

so the only option left is valves.... or a serious problem.
i had the valves adjusted about 16k miles back. i would think it should go longer between valve adjustments, but then again this was the same mechanic that forgot to put crush washers on my fuel filter which then promptly sprung a leak. sooo..... valve adjustment? maybe?