a chip isnt going to make it so you dont break anything in the engine.. actually, it will either do nothing or make it worse.

most of them just pump more fuel or air into the engine and drown it and you lose power, unless you have extensive mods and NEED a more agressive fuel curve.. in which case id recomend modding your ECU and tuning it yourself.

the ones that just remove or raise the rev limiter.. well if you dont got any mods (spcifically a hot cam, in which case you would also need some new valves/springs) then your not going to be making any power past the stock redline anyways so its pointless.. not to mention you will just throw a rod or over heat or screw up your valves or jump timing..

chips or modifying the ecu (much better than chipping) should only be done after youv got some mods done (and header, intake, cat-back doesnt count.. im talkin about cams, valves/springs, forged pistons, pnp, b+s, injectors, turbo, etc)

if you bought an ebay chip, you got scammed.. they are just $0.85 resistors that you can get at radio shack and they just make your ECU think that the car is under load, so it dumps more air/fuel in.. which makes you make LESS power and LESS gas mileage.