k i installed headers on my LO3 2night,well i cant really hook up the system for a couple days,i heard its bad to run a tbi like this...cause they run lean..is that true? and i dont have my o2 installed yet,cause my headers didnt have a way,so im putting it in 2morrow,well coming home when the car would get to the normal temp the ses light would come on,is this from not having the o2 hooked up?

Yes, you need to hook the o2 sensor up. I don't see how a lack of an exhaust system could cause the car to run lean with the o2 sensor hooked up. It would be reading the same o2 content regardless of whether there is an exhaust system attached or not because the o2 is upstream from any of that.

I've heard that it can cause premature valve wear though.

When I put my dual 3 inch exhaust on my TBI car (was getting ready for my engine swap) it didnt want to idle right anymore. It always idled a good 3-400 RPMs higher than it used to. It wasnt slower or anything... but it probably changed the volumetric efficiency a bit and my tune was off. So the same may happen to you. I ran it like taht for a couple of months with no trouble, though. Nothing broke or anything, it's not gonna hurt it. If it goes lean and starts knocking the computer will just pull timing until it's not knocking. I wouldnt worry too much about it.

If the exhaust is so short that outside air can get up to the exhaust valves it can cause them to crack from the temp difference.

well thanks everyone,but i noticed 2night when i took it to summit,it is running very rich...which is better then lean ofcourse,lol

well deff gonna hopfully get that o2 hooked up 2morrow

i mean it should help performace to shouldnt it?

It should help your motor's efficiency, that's what it was designed to do, increase your motor's efficiency at burning 1 part fuel to every 14.7 parts of air.

k i hooked up the o2 sensor and it deff help smooth out the car,but im still getting a ses light after the car warms up..but if i get on it and say take it up to like 80mph it will go away for awhile.

wat could that be?

You could start by retreiving codes and seeing WHY the light is coming on...

yea,i know..i was just seeing if this was something normal.....well guess ill check 2morrow

well the fact that it happens after it warms up tells me it is something with closed loop operation/sensors... but it could be many things, pull the code and post and we can help you from there!