2003 accord knocking problem???

I have an 03 accord w/ about 6500 miles 5sp at. And just recently noticed (because I was driving w/ the window down) that upon acceleration (w/in the 1500-2000 RPM range) my engine seems to sound like it's knocking, only for a second though...as soon as I press the gas. I did notice this only seems to happen mid-gear, and not through the entire RPM range, and also not at idle. It may also happen off the line and I just don't hear it, and does not happen when in park or neutral. It seems to occur when a load is put on the engine. May it be a gas/octane rating issue? I recently put a tank of 87 octane in. I do know that this engine is a little higher compression than the older models. May it be a timing issue, valves need adjstment? I can't see that the engine would need repairs w/ only 6500 mile on it. I don't drive it very hard, only really punch it when i need to. The car is still under warrenty for another 2 years, however so i don't get the runnaround at the dealer, I like to know in advance what s going wrong.
Any suggestions.
Thanks in advance! :banghead:

Maybe try putting some gas in from a different station, these days gas at alot of stations ends up having water in it, causing engine problems...Maybe even try a higher octane