when im at 4500 rpm at WOT, there is like a slight rattle noise from the engine, it sounds like coins rattling in a jar, somethin like that, but it only does it at high rpm

 

Sounds like youre getting some ping. What mods do you have? What fuel do you run? Does the car burn any oil?

If it is indeed ping/knock/detonation, you can try changing your fuel filter, and cleaning the wires on your MAF sensor. Also change your PCV incase that was letting oil into the intake.

 

only mods are borla catback exhaust, i run 89 octane cuz 91 is harder to get here, i am gettin ready to put 4.10s and headers on

 

Find the 91.

 

When did your car become a piggy bank??!!!

 

Yeah my brother in-law's 98 z28 doesnt run very well at all on anything but premium. Buy a bottle of the octane booster stuff and see if that helps.

 

or mix in a half gallon or full gallon of toluene or xylene available at any paint store. This will boost your octane up from 91 to roughly 94 or 95. the stuff is roughly $7 at the hardware store.

 

holy cow thats amazing i did not know, so mix some toluene or xylene in with my gas and it'll raise octane up that much, i'll try it and see if the noise goes away, is there any chance of hurting my car by putting that in?

 

Toluene is a fairly major component in premium pump gas. As long as you get the 100% pure stuff (or 99.99999%) youll be safe. Pour it in the tank before you fill up, then fill the tank with pump gas to mix it around. Its a lot more cost effective than OTC octane booster. Do some searches online (google) and youll get some opinions on the matter.