I just received a cold air intake system with no instructions for 2003 celica gt, i need instructions from someone please

its very easy. unhook the battery, take out old intake, then install new one, make sure you tighten all the clamps tight. reconnect battery, and start her up. you might notice rough performance for a few miles while your ecu learns again. if you need more detailed instructions ask or check with the manufacture.

be sure to install the O2 sensor into the little slot provided, you can seriously damage your engine if you don't remember to do this

What are you talking about?! O2 sensors in a cold air intake system? Must be a new fad. I hope you meant the MAF sensor. And that will not damage your engine, it'll just run like poop and go into limp mode and run it's default program. If it's TRD (i hope so) you may need to take apart the wheel well shield, easy. Just some 10mm screws or little push clips. Don't strip the MAF screws, just be careful and push hard to tighten them. The kits usually come with clips or wire holders and hose routers and stuff. Basically to make things simpler, everything that you take off of the old intake, be sure to back onto the new intake where it looks appropriate.

oh my mistake, i constantly mix up the flow sensor with the O2 sensor some how :(